Presentations Library

This presentation provides background and history on gravity meters, an explanation of how and why they're used at NGS, and then focuses on the principles of absolute gravity meters in particular. The presentation concludes with a description of the 2023 "International Comparison" in Boulder, CO, and other international efforts in place to ensure these instruments are accurate and consistent worldwide.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum. Part of the modernization process involves updating NGS products and services to support users of the Modernized NSRS. Such updates include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, shoreline and the many tools and datasets that make the NSRS possible. An entirely new State Plane Coordinate System is also being developed. For both the existing and future NSRS, the goal of NGS is the same: to best meet the diverse positioning needs of the entire U.S. geospatial community that includes surveyors and GIS professionals. Learn how NGS is striving towards this goal during this session.

High quality field data is a critical component of any surveying product, and the programs and modernization efforts within NGS/NOAA are supported by a team of surveyors and cartographers in the Field Operations Branch. NGS executes a variety of geodetic surveys to support the development and modernization of a wide array of critical products. This webinar will discuss recent and on-going field activities, how they support products you rely on, and give a deeper look into how complex field projects are executed. The role NGS plays in the development of the International Terrestrial Reference Frame will be described, focusing on the survey of “local ties” at colocation sites where multiple space geodetic techniques exist. This topic will explore the unique scope of work and difficulties faced when measuring between a variety of sensors at the same observatory. This overview will give the audience a better understanding of field operations at NGS and the role they play in NGS, NOAA, and international products widely used by many.

NGS's Online Positioning User Service (OPUS) provides free, easy access to the National Spatial Reference System (NSRS) by allowing users to upload their GPS data to NGS to be processed. In the past, submitting data to NGS using the Federal Geodetic Control Subcommittee (FGCS) standard titled Input Formats and Specifications of the National Geodetic Survey (NGS) Data Base (also known as the "Bluebook") was challenging. Today users can easily submit all the necessary information for loading into the database using OPUS Projects. This session will examine a few surveys in Colorado and discuss the entire process of submitting surveys to NGS including planning, proposal, execution, adjustment and submission.

NOAAss National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum.

The National Oceanic and Atmospheric Administration's (NOAA) National Geodetic Survey (NGS) has been providing the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, through improvements in technology with satellite based positioning, and other new systems of measurement that did not exist when today's National Spatial Reference System (NSRS) was developed. The modernized NSRS will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations. This course will discuss the maintenance done for today's NSRS, the NSRS Modernization efforts and how it will impact surveying in the near future.

NGS is in the process of modernizing the National Spatial Reference System (NSRS), replacing the existing horizontal and vertical datums with a suite of terrestrial reference frames and a new geopotential datum. The NSRS provides a common reference so geospatial data collected at different times by different people can be compared. A set of coordinates does not tell much without including what those coordinates are referenced to, but by specifying information about the reference system used, the data are much more meaningful. I will discuss the basics of datums and reference frames, including how they are created and how they connect at national and global levels.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum.

NSRS Modernization has, and continues to be a significant undertaking. In addition to new paradigms related to datum definitions, it has also required NGS to rethink how we collect, process, store, manipulate, and deliver data. In this session, we will review the need, and status of the major projects associated with NSRS Modernization.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum.

A lot has happened at NGS in the last year!! GRAV-D hit the 100% milestone, OPUS-Projects 5.1 was released which incorporates full Blue Booking support and the ability to import Realtime GNSS Vectors (GVX). An APLHA page was released for the new datums which highlights a preview of NCAT support, and OPUS-S 5.0 was released to BETA which includes the long awaited "M-PAGES" engine that supports multi-constellation GNSS data processing.

The NOAA (beta) SatBathy tool helps automate the creation of Satellite Derived Bathymetry (SDB) products. The current use is for reconnaissance for hydrographic surveys but once completed will help update the NOAA National Bathymetric Source (NBS) to update NOAA Charts and other shallow bathymetric needs. Today's seminar will discuss the SatBathy tool, short- and long-term plans and some of the on-going research to help support its evolution

The “2022” Datums of the Modernized National Spatial Reference System (NSRS) will be time dependent. Unlike with NAD 83 and NAVD 88, coordinates in NATRF2022 and NAPGD2022 will change with time. This talk will dig into the Passive Control for a Multi-year Corridor Project Use Case from the NGS Blueprint for the Modernized NSRS, Part 3, which looks at a hypothetical project scenario that take place over a long period of time accounts for changing coordinates in the project control. The goal of this presentation is to encourage surveyors to start considering how they will accommodate “drift” over time on long duration projects and discuss the further impacts of time-dependent coordinates with other disciplines and organizations involved in these types of projects. Part 2: The Ups and Downs of Heights and Vertical Datums: Heights are pretty simple, right? Just go up and down and watch water flow. In reality, they can be more complicated than that, and given the variety of vertical datums that are out there, it’s easy to see how important it is to understand the system you are working in. This talk will discuss the theoretical and practical aspects of vertical datums, including the different types of heights, the current height datums including NAVD 88 and IGLD (1985), upcoming changes to those datums, as well as how to work within these datums. Progress from the recent GPS on Bench Marks campaign will also be covered, as well as how the data collected in that campaign will help improve the connection between old and new datums.

GEOID2022 will be a realization of a geoid model for the North American-Pacific Geopotential Datum of 2022 (NAPGD2022). This presentation focuses on a prototype of the geoid model developed jointly by three agencies of the U.S.A., Canada and Mexico, NGS, CGS and INEGI. We will present computation procedures and methods by each agency, data compilation (terrestrial, GRAV-D airborne gravity, satellite altimetric and shipborne gravity, icesheet data, and the digital elevation model), development of the reference Earth's Gravitational Model (EGM), weighting strategy toward a single geoid model, and results of evaluation against independent data sets.

NGS’s ~15 year old Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project has finally flown every data line at least one time. This data, purposed for gravimetric geoid modeling, can be improved on and NGS intends to keep flying certain regions to improve the dataset. This webinar will include an overview of why the GRAV-D project was started, what we’ve accomplished, and a bit on how NGS collects and processes airborne gravity data. Also included, is a look at near term plans for both airborne and terrestrial gravity data collection at NGS.

Over the past year, NOAA’s National Geodetic Survey (NGS) has developed a research plan. The purpose of this document is to communicate NGS’ research and investment over both the short (i.e., next two years) and long-term (i.e., next decade) planning horizons. Providing long-term research themes allows governmental partner agencies, academic collaborators, and commercial industry insight to NGS’ plans to prepare and address the nation’s geodetic control needs for the next 10-15 years. The NGS research plan is aligned with NOAA’s FY22-26 strategic plan vision of building a climate ready nation and recognizes the intrinsic connection between weather, water, and climate systems, linked through the hydrologic cycle, driven by ocean, land, and atmospheric processes. Such long-term research requires a multidisciplinary approach, centered around geodesy using satellite observations, rooted in open science and open source methods, and driven by stakeholder needs.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum. Part of the modernization process involves updating NGS products and services to support users of the Modernized NSRS. Such updates include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. An entirely new State Plane Coordinate System is also being developed. For both the existing and future NSRS, the goal of NGS is the same: to best meet the diverse positioning needs of the entire U.S. geospatial community that includes surveyors and GIS professionals. Learn how NGS is striving towards this goal during this session.

The new National Spatial Reference System, dubbed NSRS2022, will have impacts on all of us. The presentation will provide an overall outline of the new datum, highlight some current progress, and suggest preparatory steps for engineers, surveyors, and mappers. Significant topics include geometry of the datum, design of Low Distortion Projections, retirement of the Survey Foot, and transformation of data.

The National Geodetic Survey has several million gravity data points collected over a 60 year time span. Some of these data points are located in geophysically active regions where the gravity field changes over time. In a region west of Mobile Bay, such a region was detected by airborne observations. In an effort to validate the airborne survey, a surface collection campaign was completed on a 10 km spacing over a region of 250 km by 150 km. Several absolute stations were set and relative gravity lines run across the region. Since the locations of the original could not be accurately located, a GPS-controlled survey was completed to develop a grid that spanned the same geographical region. Both grids were compared to ascertain the quality of the original data and validity of the airborne gravity. The region borders the Southern Louisiana Allochthon where a 30 year slumping event occurred. Gravity in the database pre-date the event and provide the pre-event gravity field. The newer data provide the post-event field. The difference between them is directly a function of the geophysical change over that span of time. While this span of time is significantly larger than has been addressed by GRACE modeling, the concept remains equally valid over events that occur over a much shorter period of time. Collection of a grid of gravity values develops a regional gravity field that may be compared to an earlier model to develop a gravity change field. Hence, this is a viable, if somewhat expensive, alternative to overflight by GRACE or a GRACE Follow-On mission.

OPUS Projects has matured significantly over the last few years. It has now become the primary method of submitting GNSS data to NGS for publication. The “bluebooking” process has been significantly simplified and streamlined for the user, and new standards and specifications are being developed. Additionally, OPUS Projects can now accept RTK/RTN vectors in the new GVX format. In this workshop, we will briefly discuss the history and benefits of submitting data to NGS. The majority of the workshop will be dedicated to an in-depth discussion of project planning, field procedures and the OPUS Projects processing and work flow to support project submittal to NGS. We will finish out the workshop by covering some highlights of the new standards and specifications, which will be released soon to the public.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum. Part of the modernization process involves updating NGS products and services to support users of the Modernized NSRS. Such updates include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. An entirely new State Plane Coordinate System is also being developed. For both the existing and future NSRS, the goal of NGS is the same: to best meet the diverse positioning needs of the entire U.S. geospatial community that includes surveyors and GIS professionals. Learn how NGS is striving towards this goal during this session.

Rocky Mountain Regional Update

Representatives of NOAA's National Geodetic Survey will provide an update on the fundamental improvements and needed for industry and user community preparative measures associated with the modernization of the National Spatial Reference System (NSRS). Scheduled for completion in 2025, the modernized NSRS will provide improved 3-dimensional positional accuracy through time for improved comparisons of diverse GIS data sets, development of parcel-based Land Information Systems and an array of other uses including precision navigation, intelligent transportation systems, etc.

NOAA's National Geodetic Survey is on a mission to establish a gravimetric-geoid-based geopotential datum in 2025. This work presents the latest prototype geoid model developed jointly by three agencies of the U.S.A., Canada and Mexico. Each agency is working independently using the same terrestrial gravity data, altimetric gravity and digital elevation models. In addition, the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project provides airborne gravity data covering all the U.S. territories. GRAV-D data provides critical gravity information in coastal and lake regions and areas where there is no gravity data or data with insufficient quality or distribution. The GRAV-D data was reprocessed to increase its quality and the improved gravity signal is modeled in a spherical harmonic series up to degree and order 2160. Using this spherical harmonic series as the reference field, the residual geoid is computed in the standard remove-compute-restore fashion. The geoid models are compared and validated using the GPS/leveling data collected in the Geoid Slope Validation Survey, which were conducted in 2011, 2014 and 2017. The final geoid model is then computed by weighting the individual countries' contribution. Additionally, the geoid accuracy and relative accuracy of the model are also developed. This paper reports the preliminary results of the prototype geoid model.

Modernization of the National Spatial Reference System (NSRS) is becoming a reality. Scheduled for completion in 2025, NOAA's National Geodetic Survey (NGS) is releasing preliminary ("alpha") versions of NSRS modernization products and services through a dedicated NGS alpha website. First among these is the State Plane Coordinate System of 2022 (SPCS2022). This webinar provides a preview of SPCS2022 through its various alpha products, including: 1) Preliminary SPCS2022 zone definitions, coordinates, and performance statistics. 2) NGS Coordinate Conversion and Transformation Tool (NCAT) support for SPCS2022. 3) Downloadable distortion maps and datasets used to create them. 4) Interactive web maps of SPCS2022 zone and distortion. The alpha release allows software developers, state stakeholders, and other NGS partners and customers to see SPCS2022 as it evolves toward completion. It also provides an opportunity to give feedback during the final stages of development, to ensure that SPCS2022 is an optimally designed part of the modernized NSRS.

The NSRS is built on terrestrial point-to-point angle and distance observations and future versions of OPUS will have the ability to integrate these classical observations. To enable this, NGS is developing a new XML-based file format for uploading GNSS, gravity, leveling, and classical observations to OPUS. This format, the Geodetic Data Exchange (GDX), follows the success of NGS's GNSS Vector Exchange (GVX), an XML-based format for GNSS data. GDX includes fields for point locations, metadata. This talk will share progress on GDX and highlight how classical observations will play a role in OPUS and the modernized NSRS. This includes the role of astronomical observations, including azimuths, and reduction techniques.

This presentation discusses the steps NGS is taking to make training on OPUS Projects available online. When this is complete, the mandatory requirement for live training will be removed.

The Great Lakes region is a dynamic environment, with land moving due to glacial isostatic adjustment (GIA) and large water bodies large enough to change due to short- and long-term environmental factors. The International Great Lakes Datum (IGLD) is a joint product developed by the United States and Canada to account for these changes and provide a consistent water level datum across the whole region, considering natural and manmade water level changes throughout the entire Great Lakes system. In 2022, NOAA’S National Geodetic Survey (NGS) and Natural Resources Canada's (NRC) Canadian Geodetic survey (CGS) conducted a GNSS survey across the region to observer over 350 bench marks to serve as the backbone of the new datum development. The datum, derived from this survey’s coordinates, combined with geodetic leveling ties between marks and water level sensors conducted by NOAA’s Center for Operational Oceanographic Products and Services (CO-OPS), will provide consistent ellipsoid heights on water level gauges, help determine vertical velocities of water level gauges, and assist in developing a crustal movement model. The GNSS survey conducted require immense planning, equipment, and personnel to complete within a 6-week window coordinated between both countries. The survey protocols were strict and applied correctly and much of the quality control was conducted in near real-time. Both of these steps were heavily supported by leveraging digital tools to plan, conduct, and visualize the GNSS survey. A mobile application and a data-rich webmap we employed by both field staff and managers to implement and monitor the survey results. The survey’s success will lead to project completion and provides an example to follow in the future.

The National Geodetic Survey (NGS) released "OPUS-Projects" for public use in 2011. OPUS-Projects is a web-based application designed to process and adjust campaign-style GPS observations (geodetic networks). Since the time of its release, NGS has required that users take a multi-day (approximately 12-hour) instructor-led training course before they are given access to the application. This requirement was instituted due primarily to the complexity of the application and the lack of user resource documents. It was also the case that the application was flexible enough that the inexperienced user could inadvertently direct the software to do something that would likely have unintended consequences. So, for over a decade, the National Geodetic Survey has successfully worked to train thousands of people to use OPUS-Projects. However, this training (prior to the 2020 pandemic) was conducted primarily in person, by a small number of trainers, for small groups of thirty or less. Additionally, we often heard that many companies or individuals could not afford, or did not have time to travel in order to attend a multi-day course. To partially alleviate these affordability and structural barriers, NGS initiated online, instructor-led, training courses. While NGS increased the number of online classes, these often fill up months in advance. To adequately meet the demand of our constituents following this training model would require significantly more staff time committed to registering, preparing, and teaching courses. Additionally, this training requirement prevents people from trying out the software or self-training using available resources. It is felt that this requirement has presented a barrier for use of the software, and it can be a burden for NGS to provide the training in a timely manner. This paper discusses an ongoing project aimed to develop online, self-paced training materials designed to replace the required instructor-led training, while also supplementing it with additional details. Positive outcomes of this project will include increased usage of OPUS Projects by providing unrestricted access, and the creation of a uniform curriculum focused on how to use OPUS-Projects for processing, adjusting and submitting data to NGS.

Fundamental changes are coming soon to coordinate reference systems in the United States. In 2025, NOAA’s National Geodetic Survey (NGS) will complete its modernization of the National Spatial Reference System (NSRS), the basis for U.S. surveying and mapping. That includes an update of the State Plane Coordinate System (SPCS) as the State Plane Coordinate System of 2022 (SPCS2022), a projected coordinate reference system with multiple zones covering all 56 U.S. states and territories. SPCS was originally established by NGS in the 1930s and was redefined in the 1980s as part of changing the national reference frame. SPCS2022 is the third generation of SPCS, developed to accompany the new terrestrial reference frames of the modernized NSRS. Like its predecessors, SPCS2022 consists of the three following conformal map projections: Lambert Conformal Conic, Transverse Mercator, and Hotine Oblique Mercator. An overview of SPCS2022 is provided, along with key innovations and changes from existing and previous versions of SPCS. The main change is that linear distortion (scale error) is minimized at the topographic surface rather than the reference ellipsoid surface (to reduce the difference between "grid" and "“ground" distances). To further decrease distortion in areas of high usage, population distribution was accounted for in the design process, using data from the U.S. Census Bureau. Another change is that states can have zone "layers." Every state and territory has a statewide zone to provide complete coverage with a single geometry, particularly useful for statewide Geographic Information Systems. Most states also have either one or two multiple-zone layers, each covering all or part of a state with less distortion than the statewide zone. To reduce distortion even further, 28 states designed their own SPCS2022 zones as so-called “low distortion projections” (LDPs). These LDP zones support surveying and engineering applications by making the difference between “grid” and “ground” essentially negligible. By incorporating zone layers and allowing state contributions, SPCS2022 represents a customer-driven evolution of SPCS, one that is intended to meet the wide-ranging needs of the nation’s diverse geospatial community.

Many changes are afoot as NOAA's National Geodetic Survey (NGS) moves forward with modernizing the U.S. National Spatial Reference System (NSRS). Among those changes are creation of the State Plane Coordinate System of 2022 (SPCS2022) and retirement of the U.S. survey foot. A preliminary version of SPCS2022 has been released for public comment, and the U.S. survey foot was superseded by the international foot on December 31, 2022. Although design of SPCS2022 is nearly done and the U.S. survey foot has already been deprecated, neither will be implemented by NGS until 2025, along with the rest of the modernized NSRS. This presentation gives a brief overview on the current status and rollout plans for SPCS2022, along with how and why NGS will continue to support the U.S. survey foot in the existing NSRS (but not in the modernized NSRS). In both cases, a key objective is that these changes be done in an orderly manner and with minimum disruption. To help NGS achieve that goal, your feedback is encouraged!

The National Geodetic Survey (NGS) has finished developing its web-based and freely-available surveying application, OPUS-Projects, so that users can upload GNSS vectors in the standard GNSS Vector Exchange (GVX) file format. GVX is an XML-based standard file format proposed for sharing GNSS vectors, whether derived from a real-time kinematic (RTK) survey or from post-processing. Industry is adopting GVX and providing tools in their software for exporting GNSS vectors to this format. OPUS-Projects will display the uploaded GNSS vectors in GVX both on a map and in tabular form, and it will flag vectors that do not meet user-specified quality thresholds. Moreover, OPUS-Projects will provide tools for adjusting the uploaded GNSS vectors along with any other baselines post-processed within the software in order to estimate geodetic coordinates at control points or bench marks. Users can then submit the resulting survey network adjustments to NGS for review and loading in its national database. GVX and OPUS-Projects provides an efficient means for surveyors to analyze, adjust, and publish RTK data collected on geodetic control. NGS is promoting its use by all surveyors in the United States for recovering and resurveying existing geodetic control (bench) marks as well as establishing coordinates on new control marks. OPUS-Projects uses continuous GNSS stations in the NOAA CORS Network as well as the IGS Network for aligning surveys to both the United States National Spatial Reference System and the latest global International Terrestrial Reference Frame.

The United States Department of Commerce’s National Geodetic Survey (NGS) assembles and manages the multi-purpose, multi-agency, cooperative, GPS/GNSS continuously operating reference station (CORS) network called the NOAA CORS Network (NCN). The NCN is a cooperative effort of more than 200 federal, state, academic, and private organizations, providing publicly accessible GPS/GNSS data from more than 2000 CORS, supporting post-processed positioning activities throughout the United States and its territories. 98% of these stations are owned and maintained by NCN partners. The contributing partners freely share their GNSS measurements and station information with NGS in accordance with NGS’s guidelines. NGS analyzes and archives the NCN data, and distributes it free of charge. Since its inception in 1994, the NCN has evolved into a vital national resource that provides critical positioning information for a wide range of applications, including surveying, construction, mapping and more. The NCN has undergone significant expansion over the years, with improvements in equipment and data delivery. This paper will examine the key milestones in the NCN’s history and the current state of the network.

Remotely sensed data are acquired to support NOAA’s homeland security and emergency response requirements as part of the National Response Plan Requirements are shared and received through interagency coordination that includes state and local representation The remotely sensed data collected are public domain and disseminated to federal, state, and local government agencies as well as the general public to facilitate support efforts Primary goal is the rapid delivery of geo-referenced imagery

The purpose of this webinar is to introduce NOAA Technical Memorandum NOS NGS 92, the Classification, Standards, and Specifications document which provides specific guidance for submission of survey projects for inclusion in the NGS Integrated Database using OPUS Projects 5.1.

NGS has been working on the updated NSRS for over 15 years. Too much material for two hours, but covers some of the tastier morsels during this discussion, focusing on key bits related to the rollout of the new datums.

Fundamental changes are coming soon to coordinate systems near you. In 2025, NOAA's National Geodetic Survey (NGS) will complete its modernization of the National Spatial Reference System (NSRS), the basis for surveying and mapping in the United States. Among the changes is development of the State Plane Coordinate System of 2022 (SPCS2022) to replace existing State Plane. This presentation gives an overview of key SPCS2022 characteristics and innovations, including the use of zone "layers" and low distortion projections, with emphasis on the status of zone designs in Hawai'i.

We will start with reviewing the datums that will replace NAD83 and NAVD88, what is changing but also how the future of the NSRS is somewhat similar to what you already know. Jeff will wrap up with a discussion of the major changes that SPCS2022 will bring as compared to your current SPCS83 in Pennsylvania.

Data is pretty useless if it isn't tied to a common reference. A datum is this common reference for datasets of height information. Think of it as a zero line on graph paper. Without it, the numbers you see can mean anything. The National Geodetic Survey (NGS), within the National Oceanic and Atmospheric Administration (NOAA), defines, maintains, and provides access to the National Spatial Reference System (NSRS), the coordinate system for the United States civilian federal agencies. The current vertical datum is NAVD 88, which has been in place since 1991. A complementary vertical datum, the International Great Lakes Datum (IGLD), provides reference for water levels across the Great Lakes. IGLD is jointly developed and maintained by the United States and Canada and ties to NAVD 88. In a few years. NAVD 88 is being replaced by the North American-Pacific Geopotential Datum of 2022 (NAPGD2022) while the current IGLD (1985) will be updated to IGLD (2020). I'll explain what goes into the determination of these datums, why datums get updated, and why it is critical to know what datum a dataset is tied to, regardless of the time stamp on the dataset.

NGS’s Online Positioning User Service (OPUS) provides simplified access to high-accuracy National Spatial Reference System (NSRS) coordinates. OPUS Projects gives users web-based access to simple management and processing tools for projects involving multiple sites and multiple occupations. As NGS modernizes the NSRS, these tools are being updated to better serve the needs of surveyors and other users of the NSRS. I'll discuss these recent updates to these online tools, including how to utilize GNSS vectors derived from real time network observations, as well as future goals to improve the OPUS suite of tools.

NGS’s Online Positioning User Service (OPUS) provides free, easy access to the National Spatial Reference System (NSRS) by allowing users to upload their GPS data to NGS to be processed. To use OPUS successfully, it is critical that users understand both the requirements for data input as well as what to review in the processing output. This course will describe the steps involved in processing the data using the various flavors of OPUS, will explain the output so that users can interpret and have confidence in the results and will provide some demonstrations on using OPUS.

The National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) has been providing the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, through improvements in technology with satellite based positioning, and other new systems of measurement that did not exist when today’s National Spatial Reference System (NSRS) was developed. The modernized NSRS will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations. This course will discuss the maintenance done for today's NSRS, the NSRS Modernization efforts and how it will impact surveying in the near future.

The National Oceanic and Atmospheric Administration's (NOAA) National Geodetic Survey (NGS) has provided the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, and that it is constantly changing. Today and into the future there is a need to track changes in our environment faster and with more accurate observations. This will be accomplished with a modernized NSRS that will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations. The NSRS will provide the spatial infrastructure for the future of self-driving cars, building information models, and improving flood plain mapping for the safety of life and property. The NSRS will be easier and more cost effective to maintain providing the ability to account for dynamic changes in positioning such as plate tectonics; subsurface ground fluid withdrawal induced subsidence -- in some places inches per year of vertical change; and other geophysical phenomena. This presentation will provide an update of how the future NSRS will improve and what can be done to prepare for this paradigm shift in positioning.

This is a panel discussion and we need to talk—-about your GIS data. The data must be based on something, and in the U.S. that “something” is the National Spatial Reference System (NSRS). Like Atlas supporting the entire world, the NSRS supports all U.S. civilian surveying and mapping. NOAA’s National Geodetic Survey (NGS) defines, maintains, and provides access to the NSRS. NGS is in the process of modernizing the NSRS, scheduled to occur in 2025. Among the changes is replacement of all horizontal and vertical datums with dynamic versions that account for coordinates that change over time, as well as an entirely new State Plane Coordinate System. Numerous other changes will also be made to the many NGS products and services that make building, sustaining, and using the NSRS possible. The overall aim of this panel discussion is to make you aware and ready for these changes, by providing a forum for you to ask questions and participate in conversations. In short, the goal is to help you prepare for the jolt when Atlas shrugs.

NSRS/new datums presentation for discussion during the PAIGH USNS meeting.

The National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) has provided the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, and that it is constantly changing. Today and into the future there is a need to track changes in our environment faster and with more accurate observations. This will be accomplished with a modernized NSRS that will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations. The NSRS will provide the spatial infrastructure for the future of self-driving cars, building information models, and improving flood plain mapping for the safety of life and property. The NSRS will be easier and more cost effective to maintain providing the ability to account for dynamic changes in positioning such as plate tectonics; subsurface ground fluid withdrawal induced subsidence -- in some places inches per year of vertical change; and other geophysical phenomena. This presentation will provide an update of how the future NSRS will improve and what can be done to prepare for this paradigm shift in positioning.

NGS continues its efforts to modernize the National Spatial Reference System (NSRS), which will replace the existing datums with a suite of new datums that include NAPGD2022 and NATRF2022, which will utilize time-dependent coordinates. Part 1 of this talk will focus on the new datums themselves, including how they are being developed and how surveyors will use them. Part 2 will cover recent updates to online tools that enable access to the NSRS such as OPUS Projects, which now can be used to adjust RTN-derived GNSS vectors.

The presentation describes the geometry of a low distortion projection compared to the previous design approach, shows simple visual ideas, and some sample designs for discussion.

When it comes to geospatial data, it is important to use a common reference so data collected at different times by different people can be compared. Think about it as the zero line on a graph. Changing that zero line changes the values. A set of coordinates does not tell much without including what those coordinates are referenced to. A datum or reference frame enables data to be compared. I'll cover the basics of datums and reference frames, including how they are determined and how they connect at the national and global levels.

This session will give updates on activities at NGS, including an update on State Plane Coordinate Systems of 2022 (SPCS2022), plan for new, time-dependent coordinates and how to apply them, and an update on the rollout of the new datums NAPGD2022 and NATRF2022. NGS’s online tool OPUS0Projects has also gone through some major updates, and I’ll explain how that can be used to adjust RTN- derived GNSS vectors and how that can contribute to GPS on Bench Marks to improve the new datums. This session will also present the status of the Indiana Height Modernization project.

This session will explain the various NGS products and services that work together to provide you accurate models and positions, then review our changes to NSRS modernization plans. We will also discuss the changes afoot for Pennsylvania when transitioning from SPCS83 to SPCS2022, including a review of the Pennsylvania Coordinate System Law (PL 1224, No. 161), and clarify any lingering misconceptions about the deprecation of the US Survey Foot.

The National Geodetic Survey (NGS) for over 15 years has been working on updating the National Spatial Reference Systems (NSRS). The NSRS work is simply too much for a single discussion, but I will cover some of the tastier morsels. I plan to talk about key bits related to the rollout of the new datums.

NGS is keeping the door open for GPS on Bench Mark data to be submitted for use in improving the NAVD 88 - NAPGD 2022 transformation tool through September 2023. This extension gives users an opportunity to collect observations on many more marks and take advantage of significant savings in field time by using Real Time Networks (RTN) and NGS’ new Beta OPUS Projects 5.

This is a short presentation highlighting program updates, new releases, new beta products and related topics since the last briefing.

In this episode, we talk to Lynda Bell, who is the Southwest Regional Geodetic Advisor for NOAA’s National Geodetic Survey. She is the geodetic advisor for Arizona, New Mexico, and Utah. In the episode, she explains why the National Spatial Reference Frame (NSRS) is so important and how it is a framework that ties all of our geospatial data together. She also reminds us of what a datum is and what we need to know about the new datums that are coming in 2023. She also explains the GPS on Bench Mark program and how you can contribute. We then ask her about her recent visit to Utah and the importance of the PLSS monument preservation at Temple Square and also the USGS/UGRC Great Salt Lake Causeway project - a project measuring water levels and height. You can email Lynda directly with questions at lynda.bell@noaa.gov More info from NOAA on Datums https://oceanservice.noaa.gov/facts/datum.html NOAA's National Geodetic Survey webpage https://geodesy.noaa.gov/ The GPS on Bench Marks Program https://geodesy.noaa.gov/GPSonBM/ Jack And Bore: A Key Component to Preserving the Salt Lake Temple in an Earthquake https://www.youtube.com/watch?v=N273kjZN0I8

In 2022, the Southwest Region actively supported the modernization of the National Spatial Reference System (NSRS). Constituents in the Southwest Region (AZ, NM, UT) prepared for NSRS Modernization through increased partnership activity, improvement in positioning data and imagery, building new CORS stations with improved stability and monumentation, and siting new Foundation CORS arrays at Very Long Baseline Array (VLBA) observatories in New Mexico and Arizona. Additionally, survey control was densified through partnerships that allowed for improvements in both vertical and horizontal positioning and an increase in NGS Blue Booking submissions. By increasing the accuracy of ground control, ground truthing was improved for base station positions for LIDAR, aerial, drone, photogrammetric, and altimetric data in the region. These improvements will continue to provide multiple data sets for digital elevation modeling, and become the basis for improved datum consistency as the Southwest Region prepares for NSRS Modernization.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum. Part of the modernization process involves updating NGS products and services to support users of the Modernized NSRS. Such updates include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. An entirely new State Plane Coordinate System is also being developed.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum. Part of the modernization process involves updating NGS products and services to support users of the Modernized NSRS. Such updates include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. An entirely new State Plane Coordinate System is also being developed.

Change is nearly upon us. Design of the State Plane Coordinate System of 2022 (SPCS2022) is almost done, and on December 31, 2022, the U.S. survey foot will be “deprecated.” This means that it will be deemed obsolete and should be used for historical and legacy applications only. It will be superseded by the international foot definition (i.e., 1 foot = 0.3048 meter exactly) for all applications, including SPCS2022. However, SPCS2022 will not be released until 2025, along with the rest of the modernized National Spatial Reference System. This webinar gives an overview on the status of SPCS2022 and on making an orderly transition to the international foot with minimum disruption.

This workshop will provide updated information about the planned modernization of the National Spatial Reference System (NSRS). Specifically, NGS' plans to replace the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88). This workshop will provide an opportunity for NGS to share updates and discuss the progress of projects related to NSRS Modernization, as well as new technical challenges and delays

The National Geodetic Survey’s (NGS’s) Online Positioning User Service (OPUS) provides free, easy access to the National Spatial Reference System (NSRS), by allowing users to upload their GPS data to the NGS to be processed by NGS computers. To use OPUS successfully, it is critical that users understand both the requirements for data input as well as the processing output. This course will describe the steps involved in processing data with OPUS and will explain the output so that users can interpret and have confidence in the results. We will discuss all current OPUS products to include OPUS-S, OPUS-RS, OPUS Share, and OPUS Projects.

Since the 1930s, NOAA’s National Geodetic Survey (NGS) has encouraged states to adopt the current national datum and associated State Plane Coordinate System (SPCS) in legislation. This included developing model acts to guide states in drafting legislation, initially for the SPCS 27 and then later for SPCS 83. All but one state have enacted statutes for either or both of these systems. With a modernized National Spatial Reference System (NSRS) due for rollout in 2025, NGS is again recommending that states update legislation for the new datums and the State Plane Coordinate System of 2022. A brief overview of the history and status of existing SPCS statutes is provided, along with guidance on creating new legislation. This includes a legislation template, examples of actual new statutes, “future proofing” against later changes to the NSRS, and dealing with the deprecation of the U.S. survey foot. The goal is to help ensure that what is written into state law is correctly done by users of the modernized NSRS.

This presentation provides an overview of NGS' educational and training resources.

The National Geodetic Survey and its predecessor agencies have collaborated with public and private organizations to establish reference stations at precisely determined locations over the last 200 years, setting a geodetic standard in precise positioning. NGS defines official geodetic datums for all federal mapping activities in the U.S as part of the National Spatial Reference System (NSRS). Currently the NGS is working to remove inaccuracies in the existing datums of the US. By tracking the dynamic nature of the Earth, and giving users tools to account for it, NGS will provide a new National Spatial Reference System that is semi-dynamic. To support the Modernization of the NSRS, constituents in the Southwest Region have been working to improve geodetic control and to prepare to enhance the data base that forms the foundation for the new NSRS. Teams have been working steadily in the region improving monumentation and operations of National Continuously Operating Reference Station Network (NCN) sites in partnership with NGS through braced monument workshops and the formation of new federal, state, and local partnership working groups. Additionally, four new Foundation CORS sites are being developed in partnership with NGS at Space Geodetic Observatories across the Southwest at Kitt Peak National Observatory in Arizona and at Los Alamos National Laboratory, the Pietown NRAO VLBA, and the Apache Point Observatory in New Mexico. Partners from the National Geospatial Agency, the National Radio Astronomy Observatory and the Applied Research Laboratory at University of Texas are working with NGS to begin project planning for both the NGS Foundation CORS sites and the National Science Foundation funded High Rate Tracking Receivers for Awareness of Spectrum and Timing Enhancements (HASTE) Project. The HASTE Project will provide multi-constellation GNSS observation data distributed to all project partners, improved situational awareness at NRAO's Very Long Baseline Array (VLBA) sites, improve the VLBA data quality through better timing, and support geodesy research tying the terrestrial and celestial reference frames.

In 2022 or soon after, NOAA’s National Geodetic Survey (NGS) will replace the existing State Plane Coordinate System of 1983 (SPCS 83) with SPCS2022. The new version of SPCS will be based on the 2022 terrestrial reference frames, and it will use the same ellipsoid and three conformal projection types. This presentation describes the key changes and innovations used for SPCS2022. Unlike SPCS 83, states can have zone “layers.” All states will have at least a statewide zone, and they may have up to two multiple-zone layers (although most will have only one). Also unlike SPCS 83, linear distortion (scale error) is minimized at the topographic surface rather than the ellipsoid. To further reduce distortion in areas of high usage, the NGS design process considers population distribution. A distortion design criterion envelope is established for each zone, and it includes specific percentages of population, city and town locations, and total zone area. In addition, states can design their own multiple-zone layer, which can consist of low distortion projections (LDPs). The design process used by NGS will be described, and an update will be provided on the status of SPCS2022, including LDP zones designed by state stakeholders.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS), which is a common foundation for geospatial data that serves as the basis for civilian surveying and mapping in the United States. Changes in technology and a better understanding of the dynamic earth have made it necessary to improve the NSRS to be of better use for modern applications. Currently, NGS is in the process of modernizing the NSRS, updating the existing horizontal datums with a suite of geometric reference frames and the vertical datums with a gravimetrically-derived geopotential datum. Part of the modernization process involves updating NGS products and services to support users of the Modernized NSRS. Such updates include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. An entirely new State Plane Coordinate System is also being developed.

Satellite orbit dynamics is a critical part to the Nation Geodetic Survey (NGS) infrastructure. In the age of space-based observations, it is an important concept to understand when discussing measurements taken with the Global Positioning System (GPS). Without the understanding of satellites and their produced data; GPS and other navigation systems would not work. This talk will introduce the basics of GPS and satellites while focusing on: 1) How NGS determines where satellites are in orbit and how they move. 2) Why understanding satellite orbits is important to the Global Positioning System. 3) What NGS does with created satellite data products referred to as ephemeris.

NGS’s Online Positioning User Service (OPUS) provides free, easy access to the National Spatial Reference System (NSRS) by allowing users to upload their GPS data to NGS to be processed. To use OPUS successfully, it is critical that users understand both the requirements for data input as well as what to review in the processing output. This webinar will describe the steps involved in processing data with OPUS and will explain the output so that users can interpret and have confidence in the results.

This webinar will introduce M-PAGES, the newly developed GNSS positioning software suite, which will soon be implemented in NGS applications such as OPUS. The presentation will provide some background on the modern GNSS environment and demonstrate the performance of our new software.

Status and progress of NOAA's NGS on recommendations made by the 2010 National Research Council's report entitled "Precise Geodetic Infrastructure: National Requirements for a Shared Resource."

Since 1994 the National Geodetic Survey has fostered a collaborative network of permanently installed geodetic-grade GPS reference stations, known as Continuously Operating Reference Stations (CORS). The CORS network is a multi-purpose cooperative network of GNSS observations collected from over 200 of government, academic, and private organizations. Each agency owns and operates its own stations and shares the observation data with NGS. The primary objective of the CORS network is to enable GPS users by providing precise positioning relative to the U.S. National Spatial Reference System (NSRS)- the source of official U.S. coordinates. Each CORS shares its data with NGS, and NGS in turn analyzes and distributes the data to the general public free of charge. Despite the large number of partner agencies and stations, the global reference frame stations in the US are limited due to density considerations and quality issues. In order to maintain long-term consistency between the NSRS and International Terrestrial Reference Frame (ITRF), it is desirable to maintain a set of reference frame sites to the highest standard.

NGS has planned for the construction and/or adoption of ultra-stable, high-reliability GNSS reference stations as a sub-set of the CORS program. These 36 stations will be called Foundation CORS and will become the backbone of the National Spatial Reference System. This poster presents the proposed locations of the Foundation CORS, target reliability metrics, and a plan to construct 8 new stations.

Four slides on the top priorities of NGS for updates to the NOAA CORS Network.

The largest NCN modernization project is the proposed NOAA Foundation CORS Network- an effort for the construction and/or adoption of ultra-stable, high-reliability GNSS reference stations as a sub-set of the CORS program. Our proposed partners in this effort, whose existing stations are or would be of importance to the ITRF, are NASA and NSF. The 36 identified Foundation CORS are planned to become the backbone of the U.S. National Spatial Reference System and its link to the ITRF. Following IGS efforts, we are implementing RINEX 3 and multi-constellation GNSS at our Foundation CORS and IGS stations. For the entire NCN, we are examining better metrics for determining station quality, encouraging upgrades to multi-GNSS, and planning improvements to our Online Positioning User Service. For GPS orbits, we are participating in the ITRF2020 reprocessing, implementing suggested models, and preparing for the multi-GNSS future.

Overview of the National Geodetic Survey's history and mission. How GPS works and why we need a national network of permanent GPS stations to support precise positioning applications. Beginner, non-technical audience.

NGS has planned for the construction and/or adoption of ultra-stable, high-reliability GNSS reference stations as a sub-set of the CORS program. These 36 stations will be called Foundation CORS and will become the backbone of the National Spatial Reference System. We present the proposed locations of the Foundation CORS and a plan to construct 8 new stations. Also, as of Sept 13. 2019, results of the Multi-Year CORS Solution 2 are available. You now have access to more accurate NOAA CORS Network station coordinates and velocities in both the national (NAD83) and international (ITRF) reference frames. We present highlights of the MYCS2 and plans for future modernization of the NOAA CORS Network.

Summary of NSRS Modernization plans and active work on characterizing residual ground motion, after accounting for plate motion.

NCAT update - NGS released a new version of NCAT recently. Discuss the features of the new release and a roadmap of NCAT. API update - Go over the new APIs added to the NGS API suite. Discuss web map services that are in the early development stage. JSON datasheets - NGS datasheets are captured into a ready-to-serve JSON format. This will help improve retrieval of datasheets considerably for all types of searches. In addition, users will be able to get the content in a geospatial format. Also, a web map service is planned for GIS clients. LASER - NGS built a new adjustment tool, LASER, that can be used for all types of survey projects. Mapshaper, a visualization and analysis tool, is being considered to augment LASER. Discuss the features of Mapshaper. Rinex 3 - NGS will be ingesting CORS data in Rinex 3, a new Rinex format. Discuss the benefits of Rinex 3 and a roadmap.

Modern robotic and traditional total stations and theodolites are often used to measure distance and angle using retroreflecting prisms as targets. Significant errors can result if users are unaware of the potential error sources. Presentation shows the geometry of the error sources and outlines some simple field tests to assess their magnitude.

The National Spatial Reference System (NSRS) is the common foundation shared by both surveying and GIS. NOAA’s National Geodetic Survey (NGS) defines, maintains, and provides access to the NSRS, which serves as the basis for civilian surveying and mapping in the United States. This presentation gives an overview of existing NGS products and services, and how they will change as part of NSRS Modernization. Those include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. But the NSRS is not static; it must evolve as positioning technology and our understanding of the dynamic Earth improve. Among the changes coming within the next few years is replacement of the current U.S. horizontal and vertical datums, including an entirely new State Plane Coordinate System. For both the existing and future NSRS, the goal of NGS is the same: to best meet the diverse positioning needs of the entire U.S. geospatial community that includes surveyors and GIS professionals.

The National Spatial Reference System (NSRS) is the common foundation shared by both surveying and GIS. NOAA’s National Geodetic Survey (NGS) defines,maintains, and provides access to the NSRS, which serves as the basis for civilian surveying and mapping in the United States. This presentation gives an overview of existing NGS products and services, and how they will change as part of NSRS Modernization. Those include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. But the NSRS is not static; it must evolve as positioning technology and our understanding of the dynamic Earth improve. Among the changes coming within the next few years is replacement of the current U.S. horizontal and vertical datums, including an entirely new State Plane Coordinate System. For both the existing and future NSRS, the goal of NGS is the same: to best meet the diverse positioning needs of the entire U.S. geospatial community that includes surveyors and GIS professionals.

In the Fall of 2021, NGS performed a field campaign in south-central Alaska to obtain geodetic observations that will be used by the Geoid Monitoring Service (GeMS) to validate time-dependent geopotential models (geoid, gravity, deflection of the vertical). The observations collected are critical to GeMS and a time-dependent geoid model in order to evaluate two situations: 1) to assess how much geoid change has occurred since 1964, when the Coast and Geodetic Survey performed a very high-accuracy triangulation, leveling, and gravity survey following the 1964 Alaska Earthquake; and 2) to establish a baseline to measure all subsequent geoid change against in the future.

Overview of the NSRS modernization effort, its impact on water-related modeling efforts, and ways to prepare for the future modernized NSRS.

NOAA’s National Geodetic Survey has responded to emergency events with medium format digital cameras since 2003. Within hours of landing the plane, aerial imagery is distributed through NOAA's Emergency Response Viewer to aid first-responders, federal and local governments, and the public. This webinar will cover tips on using the emergency response viewer, the unique challenges faced during past hurricane seasons, and frequently asked questions from the public. Imagery applications will also be discussed.

An overview of how the NSRS was developed, its current status and how it is being updated, and how it will impact GIS users.

NGS is now providing tools that support the use of real-time kinematic (RTK) data in control survey projects. NGS has released Beta OPUS-Projects 5 where users can upload RTK vectors in a newly defined standard file exchange format called GVX. A demonstration will be given on how to set up an RTK rover, export the data to GVX format, and upload the GVX file to OPUS-Projects 5 for inclusion in a survey network for least squares adjustment. Additional discussion will be given on the recommended RTK field practices, how to prepare an RTK survey on bench marks for publication at NGS, and how to use quality control and adjustment tools inside of OPUS-Projects 5.

Astronomy has played a central role in geodesy, whether through measuring Earth’s shape or precisely orienting geodetic networks. This webinar introduces the basic concepts of geodetic astronomy. It overviews the methods and practices of the Coast & Geodetic Survey throughout the 19th and 20th century and the role geodetic astronomy played in the development of modern geodetic systems. It closes with the story of modern geodetic astronomy at NGS with the Geoid Slope Validation Surveys and the development of the Total Station Astrogeodetic Control System (TSACS).

The National Spatial Reference System (NSRS) is the common foundation shared by both surveying and GIS. NOAA’s National Geodetic Survey (NGS) defines, maintains, and provides access to the NSRS, which serves as the basis for civilian surveying and mapping in the United States. This presentation gives an overview of existing NGS products and services, and how they will change as part of NSRS Modernization. Those include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. But the NSRS is not static; it must evolve as positioning technology and our understanding of the dynamic Earth improve. Among the changes coming within the next few years is replacement of the current U.S. horizontal and vertical datums, including an entirely new State Plane Coordinate System. For both the existing and future NSRS, the goal of NGS is the same: to best meet the diverse positioning needs of the entire U.S. geospatial community that includes surveyors and GIS professionals.

The National Spatial Reference System (NSRS) is the common foundation shared by both surveying and GIS. NOAA’s National Geodetic Survey (NGS) defines, maintains, and provides access to the NSRS, which serves as the basis for civilian surveying and mapping in the United States. This presentation gives an overview of existing NGS products and services, and how they will change as part of NSRS Modernization. Those include coordinate conversions and transformations, geodetic control, GNSS data processing, the Continuous Operating Reference Station (CORS) network, aerial imagery, and the many tools and datasets that make the NSRS possible. But the NSRS is not static; it must evolve as positioning technology and our understanding of the dynamic Earth improve. Among the changes coming within the next few years is replacement of the current U.S. horizontal and vertical datums, including an entirely new State Plane Coordinate System. For both the existing and future NSRS, the goal of NGS is the same: to best meet the diverse positioning needs of the entire U.S. geospatial community that includes surveyors and GIS professionals.

A discussion on all of the different components of NOAA's National Geodetic Survey Online Positioning User Service (OPUS).

NGS provides a team of Regional Geodetic Advisors, living and working in regions across the United States, who are available to assist you with questions or problems related to the National Spatial Reference System (NSRS). Whether it be questions about establishing a CORS, using OPUS, collecting data for GPS on BenchMarks (GPSonBM), or providing a presentation at your conference, your Regional Advisor is well equipped to facilitate. Please join us for an explanation of the NSRS and an update on the Advisor Program!

An overview of the NGS Tools and Projects that support the current datum and build toward the new datum. Focus is on the existence and location of the information on the NGS website. If one or more of the topics sparks interest, the presentation will guide the user to the resources needed.

GPS on Bench Marks is a crowd sourced data collection effort to help communities across the Nation prepare to transition to, and reap the benefits of, the Modernized National Spatial Reference System (NSRS) that NGS will release in the next few years. One crucial component of NSRS Modernization is for NGS to provide national scale tools that will allow users to transform their existing data between the current system and the Modernized NSRS. GPSonBM participants across the country collect GPS data on historic NGS survey control monuments and submit that data to NGS to improve the local accuracy of NGS’ national-scale Transformation Tools. NGS has extended the cut-off date to submit GPS on Bench Mark data for use in the 2022 Transformation Tool until December, 31st 2022. This extension reflects NGS’ commitment to include as much local data as possible in creating the transformation tool. It also gives participants an opportunity to submit much shorter RTK or RTN observations on marks through the new beta version of OPUS Projects 5.0. This webinar will kick off 2022 by featuring two inspiring guest stars, Mick Heberlein from Wisconsin DOT, and Jacob Heck, the NGS Great Lakes Regional Geodetic Advisor. In addition to a general overview and look ahead from GPSonBM Program manager Galen Scott, Jacob and Mick will talk about how they teamed up to encourage participants across the State to complete observations on nearly all of the priority bench marks in Wisconsin in 2021. Their story will provide a roadmap for others across the country to take advantage of this extra year of data collection and prepare their communities to derive the full suite of benefits from the Modernized NSRS to come.

The primary objective of the 1-cm geoid experiment in Colorado (USA) is to compare the numerous geoid computation methods used by different groups around the world. This is intended to lay the foundations for tuning computation methods to achieve the sought after 1-cm accuracy, and also evaluate how this accuracy may be robustly assessed. In this experiment, (quasi)geoid models were computed using the same input data provided by the US National Geodetic Survey (NGS), but using different methodologies. The rugged mountainous study area (730 km 550 km) in Colorado was chosen so as to accentuate any differences between the methodologies, and to take advantage of newly collected GPS/leveling data of the Geoid Slope Validation Survey 2017 (GSVS17) which is now available to be used as an accurate and independent test dataset. Fourteen groups from thirteen countries submitted a gravimetric geoid and a quasigeoid model in a 1' 1' grid for the study area, as well as geoid heights, height anomalies, and geopotential values at the 223 GSVS17 marks.

The State Plane Coordinate System of 2022 (SPCS2022) is nearing completion. Next steps include finishing the design reviews and getting stakeholder feedback, with a target of finalizing SPCS2022, fittingly, in the year 2022 itself. SPCS2022 is part of modernizing the National Spatial Reference System (NSRS). Although zone definitions will be available in 2022, its official rollout will occur later (along with the rest of NSRS Modernization). This presentation gives a preview of what to expect for SPCS2022, which is a mix of zones designed by NGS and by state stakeholders. Based in the current status of the project, SPCS2022 will consist of: • About 160 zones designed by NGS • Over 800 zones designed by stakeholders in 28 states • A single “statewide” zone for every state and territory • One or two additional multiple-zone “layers” for 38 states • Three “special use” zones that extend into more than one state Preliminary designs will be provided for public review in early 2022 and finalized later that year. Completing SPCS2022 early will give the geospatial community more time to prepare for this key component of NSRS Modernization.

This User Forum addresses sharing your OPUS solutions, and includes an update on the GPS on Bench Marks campaign. Several demos are shown, and we discuss some common reasons submissions to OPUS Shared Solutions may fail. The remainder of the time is spent on a question and answer period on any OPUS topics.

An overview of the International Great Lakes Datum, including its definition and planned updates. This talk covers hydraulic correctors, dynamic heights, orthometric heights, and instrumentation that is used in datum definition and access.

An overview of the status of NSRS Modernization as of September, 2021, with an in-depth explanation of new coordinate types in the Modernized NSRS.

To accommodate planned changes associated with modernization of the National Spatial Reference System (NSRS), the CORS team is reexamining requirements of the NCN and CORS program. During this webinar, the presenters will give a brief (~20 min) description of: 1.) the current services provided by the NCN and CORS Program, and 2.) an update on planning efforts to update the NCN and CORS Program in order to meet the needs of the modernized NSRS. The presentation will be followed by ~60 minutes of discussion allowing stakeholders to ask questions and provide input. Specifically, we want to understand NCN partner and user requirements so they can be accounted for in the planning efforts.

NOAA's National Geodetic Survey (NGS) defines, maintains, and provides access to the National Spatial Reference System (NSRS). Here we overview NGS products and services, and how they will change as part of NSRS Modernization. (part I,Lynda Bell)

This webinar will highlight many of the geospatial resources available for viewing, analyzing and downloading data from the National Geodetic Survey. This webinar will highlight several NGS web maps, including the NGS Data Explorer, OPUS Share Map, and GPS on Bench Marks web map. It will also highlight data files and web services that feed these maps and how to access them. Many of these services are available in ArcGIS Online (AGOL), which allows users and other organizations to add this data to their own web maps for discovery and analysis.

This presentation provides an overview of the GitHub platform, how to access the software hosted on GitHub, and how to contribute to the software through enhancements. NGS uses the GitHub platform to make NGS software available to the public and help promote collaboration. The presentation also provides an overview of the NOAA big data platform, what’s available there, and how to access it.

NOAA's Continuously Operating Reference Stations (CORS) Network provides Global Navigation Satellite System (GNSS) data to support three-dimensional positioning, meteorology, space weather, and geophysical applications throughout the United States. This webinar provides an overview of the NOAA CORS Network-the people, agencies, and infrastructure behind it- and the efforts underway to improve and modernize it.

This presentation gives a brief (10-minute) overview of new functionality available in the latest version of OPUS Projects. This functionality enables users to run all the necessary network adjustments and load all supporting files to successfully submit a campaign-style GPS survey to NGS for publication.

-Update the current status of NGS's NSRS Modernization effort. -Provide a brief description of the new horizontal and vertical datums. -Review the status of the new layers and the corresponding zones for the State Plane Coordinate System (SPCS) in Washington. -Time for Q/A

This webinar will provide an update on the GPS on Bench Marks program’s progress toward the ambitious goals set for the 2022 Transformation Tool Campaign and the role the program is playing in preparing communities to take full advantage of the benefits of the modernized NSRS to come. We will highlight recent advances, recap the data received so far, review the existing tools, and explore remaining data gaps to focus participants’ efforts in 2021.

In 2022, the US National Geodetic Survey will introduce a geoid model to serve as the basis for a new geopotential datum. Because the geoid changes in time, this model must account for geoid change signals of more than 1 cm on the timescale of a decade to maintain its accuracy. The GRACE mission provided monthly geopotential solutions that may be converted to geoid trends at ~300 km resolution, which is adequate for capturing most geopotential change in North America. However, highly localized ice mass loss from mountain glaciers in Alaska produces geoid change signals exceeding 2 mm yr-1 at higher spatial resolution than GRACE can capture, with truncation effects attenuating peak geoid change amplitudes by a factor of 2. Additionally, the terrestrial gravity and leveling datasets used to construct and verify the static geoid model were taken over many decades and contain signals of uplift and geoid change at the decimeter level. To predict present-day geoid change, we combine Goddard Space Flight Center mascon solutions with high-resolution ice mass loss rates developed with data from ICESat, ICESat-2, and airborne lidar missions to generate high-resolution predictions of geoid change. These models are verified against dense GNSS bedrock velocity measurements and tide gauge records. We examine the resolution improvement offered by the Goddard L1B regression trend mascon solutions. Finally, we use comparisons of modern altimetry with aerial photogrammetry from the mid-20th century to develop models of past geoid change and verify these predictions against tide gauge records, leveling, and terrestrial gravity observations.

NGS is developing OPUS-Projects so that GNSS vectors, including those from real-time kinematic (RTK) surveys, can be uploaded to a survey network for least-squares adjustment and submittal to NGS for publication. This has required developing a standardized GNSS vector exchange format known as GVX.

Discussion topics on how to best continue engagement between NGS and Industry partners as the products and services of the Modernized NSRS are developed.

Presentation covers data formats that NGS will provide in the Modernized system, and the platforms NGS will use to deliver the data.

NGS is adopting Github as a repository for sharing source code and related files and documentation for major NGS products such as NCAT, VDatum, OPUS, and the Geodetic Toolkit. This will help to ensure that partners in the geospatial industry have access to NGS' latest implementations of authoritative code and can be alerted when NGS makes changes.

These slides show the participants in the 2021 Industry Workshop for NSRS Modernization. For NGS, participant names, Divisions, and roles for industry engagement are listed. For private sector, participant names, company names, and job titles are shown.

Transitioning to, and fully realizing the benefits of the Modernized National Spatial Refence System will require the submission of survey data to NGS for building of tools and computing new coordinates. In today’s connected world, sharing data is relatively easy and straightforward. By harnessing the power of crowd-sourcing data from the geospatial community, while still maintaining our robust standards and quality control efforts, we can improve our authoritative models and tools and enhance access to the Modernized NSRS for all of our common stakeholders. NGS encourages industry partners to make it easy for their users to share data with NGS and receive the new "Tied to the NSRS" designation that will be available through OPUS 6.0

This presentation will provide an overview of NGS’ effort to modernize the NSRS, including the status and timelines of ongoing projects. It will also review recent updates to “blueprint” publications about defining the new reference frames and geopotential datum and working in the modernized NSRS.

NGS has been collecting airborne gravity data since ~2008 for the purpose of modeling a geopotential surface to redefine the way heights (elevations) are determined. The goal of this effort, the GRAV-D project, is to collect airborne gravity data over the entire US and its territories. GRAV-D is just over 85% complete, but much work remains, including some remote regions in the Pacific. We have made major progress in Hawaii and have been able to negotiate some challenging airspace in southwest CONUS. We tentatively have plans to collect data over the Aleutian Islands this spring and summer as well.

From 2014 to 2020, NGS published annual experimental geoid (xGEOID) models. These models contain the gravity data from the latest satellite gravity models, the terrestrial gravity, and most importantly, the airborne gravity from the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project. The xGEOIDs provide a preliminary but increasingly-accurate view of the changes expected from the upcoming North American-Pacific Geopotential Datum of 2022 (NAPGD2022). This talk will provide the current status of the xGEOID modeling, and a brief introduction to the Colorado geoid experiment, which has been an international effort to compare and validate geoid computation methodologies.

The National Geodetic Survey (NGS) is in the process of modernizing the National Spatial Reference System (NSRS), which includes replacing the horizontal datum NAD 83 with a suite of terrestrial reference frames (including NATRF2022) as well as updating the State Plane Coordinate Systems. This session will focus on NGS’s efforts to replace NAD 83 with modernized geometric reference frames. We will cover a technical background on global and national reference frames (including ITRF) and how they relate with each other. We will also show how surveyors will work in the new reference frames.

NGS is in the process of modernizing the National Spatial Reference System (NSRS), preparing to replace the horizontal datum NAD 83 with a suite of terrestrial reference frames (including NATRF2022), the vertical datum NAVD 88 with a geopotential datum NAPGD2022, as well as updating the State Plane Coordinates Systems. This talk will provide background on reference frames and geopotential datums and give an overview of the products and services that NGS provides to the Surveying community. It will then discuss NGS’s efforts to modernize the NSRS including the latest news related to them. The talk will also show what you can do to help NGS improve the new NSRS through activities such as GPS on Bench Marks.

NGS performed three ground truth surveys to test geoid models in various terrains: relatively flat, low elevation (Texas 2011), higher, undulating terrain (Iowa 2014), and finally, high, mountainous terrain (Colorado 2017). Results indicate that the shape of the geoid can be determined to 1cm, 2cm, and 4cm in these regions, respectively. I’ll discuss the overall idea, the surveys, the analysis, and the conclusions, and what it all means for determining heights in the new National Spatial Reference System.

NGS is retooling its in-house software to use data from all GNSS constellations. This new software suite, named M-PAGES (i.e., Multi-GNSS PAGES), will be incorporated into all Modernized NSRS products and services. This talk reviews M-PAGES progress to date and preliminary results.

NGS has contracted with Polaris Geospatial Services to write an entirely new, do-it-all Least Squares Adjustment software suite. This new LSA suite will replace all existing LSA code in current use around NGS and will be incorporated into all Modernized NSRS products and services. This talk will cover the motivation and current status of that project.

The State Plane Coordinate System (SPCS) was created by NGS in the 1930s for surveyors and engineers. SPCS has since been adopted by many others in the geospatial community, and their input is contributing to a major update as part of NSRS Modernization. This presentation briefly describes how SPCS will change and the role of NGS customers in its evolution.

This presentation is a short tale of two feet. Since 1959, two nearly identical versions of the foot have been used in the U.S., resulting in costly errors. On December 31, 2022, the “old” U.S. survey foot will be retired and the “new” international foot will be the only officially recognized definition, including for the future State Plane Coordinate System.

NGS will automatically reprocess shared data and provide new 2020.0 Reference Epoch Coordinates when the Modernized NSRS is released. NGS will also provide a transformation tool to enable conversions from current datums to new reference frames and geopotential datum. The ongoing GPS on Bench Marks campaign will help improve the future transformation tool and enable local partners to prepare to take full advantage of the benefits of the modernized system.

NSRS Modernization will better account for land motion over time, while also supporting customer needs, which temporarily must assume positions remain "constant." Two types of coordinates will be used to implement this dual-track approach: Survey Epoch Coordinates (SECs) and Reference Epoch Coordinates (RECs).

Information technology improvements, combined with the expansive amount of geodetic and visual information available for geodetic survey marks requires NGS to modernize our data delivery system to best meet the future needs of our customers.

A recent update to OPUS allows users to submit their static GPS data for inclusion in the NGS Integrated Database. We will soon add the capability to submit GNSS vectors from RTK, RTN (aka VRS), or post-processed surveys. These features and the future of OPUS will be explained.

NGS plans to continue adding functionality to its popular OPUS suite, and we believe it will remain a critical tool used by surveyors to work in the NSRS. Future improvements will include automated recommendations such as what are the best continuously operating reference stations (CORSs) to use as control in a project.

Advances in GNSS and the added functionality planned for OPUS will require the introduction and adoption of new formats for data submission. This session will discuss common data formats that NGS is pursuing, in coordination with industry and other global standards organizations. Examples of data formats that will be discussed include RINEX3 and GVX.

NGS has developed four applied use cases to provide users a window into what it will be like to work in the modernized NSRS. These use cases are intended to facilitate stakeholder feedback about necessary products or training, and serve as a starting point for those interested in pursuing detailed data-driven cases studies in the future. The thought experiments are framed around: Flood Mapping, Passive Control for a Multi-year Corridor Project, Transitioning Data to the Modernized NSRS, and Airport and Other Infrastructure Monitoring.

The National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) has been providing the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, through improvements in technology with satellite based positioning, and other new systems of measurement that did not exist when today’s National Spatial Reference System (NSRS) was developed. The modernized NSRS that will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations.

The National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) has been providing the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, through improvements in technology with satellite based positioning, and other new systems of measurement that did not exist when today’s National Spatial Reference System (NSRS) was developed. The world is in constant change and there is a need to track changes in our environment with faster and more accurate observations. This can be accomplished with a modernized NSRS that will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations. The NSRS will provide the spatial infrastructure for the future of self driving cars, building information models, and improving flood plain mapping for the safety of life and property. The NSRS will be easier and more cost effective to maintain providing the ability to account for dynamic changes in positioning such as plate tectonics; subsurface ground fluid withdrawal induced subsidence – in some places inches per year of vertical change; and other geophysical phenomena. This presentation will provide an update of how the future NSRS will improve and what can be done to prepare for this paradigm shift in positioning.

The U.S. National Geodetic Survey (NGS) has historically processed dual-frequency GPS observations in a double-differenced mode using the legacy software called the Program for the Adjustment of GPS Ephemerides (PAGES). As part of NGS’ modernization efforts, a new software suite named M-PAGES (i.e., Multi-GNSS PAGES) is being developed to replace PAGES. M-PAGES consists of a suite of C++ and Python libraries, programs, and scripts built to process observations from all GNSS constellations. The M-PAGES team has developed a single-difference baseline processing strategy that is suitable for multi-GNSS. This approach avoids the difficulty of forming double-differences across systems or frequencies, which may inhibit integer ambiguity resolution. The M-PAGES suite is expected to deploy to NGS’ Online Positioning User Service (OPUS) later this year. Here, we present the processing strategy being implemented along with a performance evaluation from sample baseline solutions obtained from data collected within the NOAA CORS Network.

NGS has developed four applied use cases to provide users a window to what it will be like to work in the modernized NSRS. Thought experiments framed around (1) Flood Mapping, (2) Passive Control for a Multi-year Corridor Project, (3) Transitioning Data to the Modernized NSRS, and (4) Airport and Other Infrastructure Monitoring showcase how features of the modernized NSRS can be leveraged in familiar and new workflows. These use cases are intended to facilitate stakeholder feedback about necessary products or training, and serve as a starting point for those interested in pursuing detailed data-driven cases studies in the future.

The National Oceanic and Atmospheric Administration's (NOAA) National Geodetic Survey (NGS) has been providing the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, through improvements in technology with satellite based positioning, and other new systems of measurement that did not exist when today's National Spatial Reference System (NSRS) was developed. The modernized NSRS that will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations.

Astronomical measurements of the deflection of the vertical offer unambiguous, robust indications of the shape of the geoid. Compared with popular methods of geoid measurement, such as GNSS/leveling and gravimetry, astrogeodetic data can also be gathered rapidly and cost-effectively. Astrogeodetic methods are therefore a desirable complement to these techniques. NOAA's National Geodetic Survey has developed an astrogeodetic measurement system for the Leica TS60 imaging robotic total station. This total station is distinguished by its built-in image sensor, which eliminates the need for an external image sensor and modifications to the total station's optics. The total station's observation sequence is coordinated with inexpensive peripheral hardware. During an observation session, a microcontroller communicates with the total station and controls its movements, directing it to capture video of selected stars with GPS-referenced timing. The video, total station orientation, and timing data captured by the system are later analyzed to measure the elevation angles of the target stars and estimate astronomic latitude and longitude. Initial results suggest an accuracy better than ±0.2 arcseconds, which is sufficient for geoid validation and datum orientation. In this work, we characterize the suitability of the Leica TS60 for astrogeodetic observations; describe the hardware and software that coordinate data collection and analysis; and characterize the performance of the instrument using comparisons to historical measurements. The accuracy achieved with low-cost control hardware and rapid data collection distinguishes this project from other astrogeodetic systems.

Dynamic heights are useful for applications involving the flow of water and determination of heights above water surfaces. Water flows "down," because the geopotential energy that was stored is released. These lower surfaces actually have a greater geopotential value as you move closer to the center of the Earth. Hence, models of the Earth's geopotential field can be used to evaluate the water flow by determining dynamic heights. Dynamic heights are scaled geopotential values usually determined by dividing by a constant value for gravity (e.g., normal gravity value at 45 degrees latitude). Dynamic heights determined along a river or lake surface can be compared to actual river/lake datums or observations at water stations. This approach has been examined previously on larger bodies of water (the Great Lakes) but also has applicability in other regions, which are examined here.

The GDA has begun to be implemented. It impacts 16 US Departments and subordinate Agencies. It requires adoption of the ITRS per international agreement of the GGRF. WGS84 is no longer suffices.

Federal Real Property should be recorded in the NSRS and not WGS84. The GDA provides significant motivation to do this.

Upcoming suppression of orthometric heights on NGS datasheets in southeast Texas

A common geodetic framework must be defined and used in order to obtain optimal results from disparate Earth system datasets

TX Control issues, Datasheets, Heights Suppression and new Primary Network design, considerations for a Ht Mod Survey and how to conduct a GPS Campaign

A 50 minute presentation giving a short history of U.S. horizontal / geometric datums and the coming new 2022 datum. Also provides why it is necessary to move on from NAVD88 to NAPGD2022 and generally how that will be accomplished. Presentation provides update on the new 2022 datums, the 2022 SPCS Project, and deprecation of the US Survey Foot.

A 45 minute presentation giving a short history of U.S. horizontal / geometric datums and the coming new datum in 2022. Also provides why it is necessary to move on from NAVD88 to NAPGD2022 and generally how that will be accomplished. Presentation provides update on the new 2022 datums, the SPCS Project for 2022, deprecation of the US Survey Foot.

Until recently, users wishing to submit their campaign-style GPS survey to NGS for inclusion into the NGS Integrated Database needed to go through session processing and network adjustments using the PC executables PAGES and ADJUST, and meticulously follow all steps of file creation and management known as “bluebooking.” The latest version of OPUS Projects offers an alternative path for achieving the same result, but via an intuitive, user-friendly web application that users have come to know as OPUS Projects. The new OPUS Projects supports all users, not just those interested in submitting their data to NGS.

a brief description of many planned Online Positioning User Service (OPUS) tool enhancements, including OPUS-S and OPUS-Projects.

NGS has calibrated GPS user antennas since 1994, and recently added multi-GNSS capability with absolute calibrations. This talk reviews receiver antenna calibrations at NGS and presents some absolute calibration results. Antenna calibrations must be applied for accurate GPS/GNSS positions, especially heights.

This webinar describes how NGS collects coastal mapping data, and the many ways the data are used. NGS delineates the national shoreline through various photogrammetric sources, including tide-coordinated stereo aerial photographs, commercial satellite imagery, Light Detection and Ranging (LiDAR), and related remote sensing technologies. The national shoreline provides critical baseline data for updating nautical charts; managing coastal resources; and defining U.S. territorial limits, including the Exclusive Economic Zone. It supports: maritime trade and transportation, coastal and marine spatial planning, coastal engineering, academic research, and insurance activities, to provide a means for enhancing global competitiveness and for more efficiently managing resources.

This webinar provides an update on the GPSonBM program's progress toward the ambitious goals set for the 2022 Transformation Tool Campaign and the program's broader role in preparing for the modernized NSRS. We recapped the data received so far, reviewed the existing tools, and explored remaining data gaps to focus participants' efforts in 2021.

Since the SOS was first installed at the NOAA HQ in Silver Spring I developed National Geodetic Survey data visualizations for SOS to help inform decision-making constituents, employees and guests about our products and services. NGS will be updating the National Spatial Reference System (NSRS) in upcoming years and this platform has provided a unique opportunity to show some of the expected changes and data collections done to help enhance NOAA and SOS visualizations and share my experiences creating data visualizations, giving presentations and showcasing the SOS for VIP audiences.

The mission of NOAA's National Geodetic Survey (NGS) is to define, maintain, and provide access to the National Spatial Reference System (NSRS), the foundation for navigation, mapping, and surveying in the United States. For most of its over 200 year history, NGS has largely met its mission objectives without GIS...until recently. NGS has been developing more tools and applications to help analyze and visualize geospatial data for both internal and external use. This presentation will describe some of these new NGS GIS products and services and how these new tools provide better access to the NSRS leveraging the power of GIS for display and analysis of geodetic data. By developing such products, NGS better meets the needs of our growing and diverse customer base of surveyors, GIS practitioners, and other geospatial professionals.

The National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) has been providing the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, through improvements in technology with satellite based positioning, and other new systems of measurement that did not exist when today’s National Spatial Reference System (NSRS) was developed. The world is in constant change and there is a need to track changes in our environment with faster and more accurate observations. This can be accomplished with a modernized NSRS that will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations. [[ The NSRS will provide the spatial infrastructure for the future of self driving cars, building information models, and improving flood plain mapping for the safety of life and property. The NSRS will be easier and more cost effective to maintain providing the ability to account for dynamic changes in positioning such as plate tectonics; subsurface ground fluid withdrawal induced subsidence – in some places inches per year of vertical change; and other geophysical phenomena. ]] This presentation will provide an update of how the future NSRS will improve and what can be done to prepare for this paradigm shift in positioning.

The National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) has been providing the positioning infrastructure for the nation since 1807 when Thomas Jefferson created the Survey of the Coast. Society continues to learn more about how dynamic our world is, through improvements in technology with satellite based positioning, and other new systems of measurement that did not exist when today’s National Spatial Reference System (NSRS) was developed. The world is in constant change and there is a need to track changes in our environment with faster and more accurate observations. This can be accomplished with a modernized NSRS that will provide a precise, consistent and accurate positioning infrastructure that is readily and easily accessible primarily through Global Navigation Satellite System (GNSS) observations. [[ The NSRS will provide the spatial infrastructure for the future of self driving cars, building information models, and improving flood plain mapping for the safety of life and property. The NSRS will be easier and more cost effective to maintain providing the ability to account for dynamic changes in positioning such as plate tectonics; subsurface ground fluid withdrawal induced subsidence – in some places inches per year of vertical change; and other geophysical phenomena. ]] This presentation will provide an update of how the future NSRS will improve and what can be done to prepare for this paradigm shift in positioning.

Using Colorado's mountains as examples of "height above sea level", I discuss the current vertical datum (NAVD88) and its eventual replacement, NAPGD2022. I explain how orthometric heights will be derived from GNSS measurements and a geoid model. I end with a discussion of using atomic clocks for geodesy in the future.

The presentation was focused on the current state of geodetic control (with emphasis on vertical control issues) in the southeast Texas, and what can be done to densify the local geodetic control network with good heights.

NGS attended meetings with various TX agencies in Austin and Houston to discuss the current state of geodetic control (with emphasis on vertical control issues) in the southeast Texas. The discussions were focused on what can be done to densify the local geodetic control network with good heights.

The U.S. National Spatial Reference System is aligned with the International Terrestrial Reference Frame. This presentation discusses what that statement means, why it is done, and how it is achieved.

Brief overview of NGS and the importance of geodesy, the National Spatial Reference System (NSRS), and the NSRS Modernization effort.

NGS has developed a web-based, freely available tool named OPUS-Projects for processing and adjusting GNSS survey projects. The tool facilitates the management of multiple GNSS measurements taken on more than one mark. OPUS-Projects provides CORS for use as control, and it references surveys to the NSRS. Recent developments allow streamlined submission of GNSS surveys to NGS for review and publication. In addition, work is underway to allow end-users to upload GNSS vectors from real-time kinematic (RTK) surveys for quality assessment and least squares adjustment. Thus, OPUS-Projects is becoming an efficient tool for surveyors to establish geodetic control with GNSS.

The mission of NOAA's National Geodetic Survey (NGS) is "to define, maintain and provide access to the National Spatial Reference System (NSRS), the national system of latitude, longitude, elevation (along with related models and tools), which comprise the nation's foundational positioning infrastructure. For several years now, NGS has been developing - and promoting – a modernized NSRS, that will replace the current U.S. horizontal and vertical datums. This presentation will provide an update on the progress toward the modernized NSRS, talk about the use of the recently released NGS coordinate conversion & transformation program, NCAT, compare NCAT to previous NGS transformation programs, while also providing information on preparing for the new datums.

A review of gravimeters NGS has used in past 35 years, absolute gravimeter locations, GRAV-D and research. Introduction of 2022 datums.

This PDF binder file contains the five presentations given at the FGCS Meeting October 25, 2018.

Contains instructions and best practices on how to submit and share GPS observations on bench marks in support of the GPS on BM campaign and development of the vertical datum transformation tool.

The NGS Coordinate Conversion and Transformation Tool (NCAT) allows easy conversion between coordinate systems and/or transformation among different reference frames/datums, in a single step. This webinar gives an overview of NCAT capabilities, with high-level information on the transformations "under the hood".

The NGS Coordinate Conversion and Transformation Tool (NCAT) allows easy conversion between coordinate systems and/or transformation among different reference frames/datums, in a single step. This webinar gives an overview of NCAT capabilities, with high-level information on the transformations "under the hood".

The State Plane Coordinate System (SPCS) of tomorrow is taking shape. March 31, 2020 was the deadline for submitting requests and proposals for SPCS2022 zones. Requests are for designs by NGS, and proposals are for designs by state stakeholders. Inquiries were also received for "special use" zones with coverage areas in more than one state. This presentation shows how stakeholder input affects the number, distribution, and performance of SPCS2022 zones. Although there will be more zones than earlier versions of SPCS, that will vary greatly by state, with some having only one zone and others having many zones (including low-distortion projections). This variability shows how SPCS2022 will help meet the diverse needs of the geospatial communities in different states.

This webinar provides an overview of the FAA Airports Surveying GIS (AGIS) Program and AGIS website, emphasizing the collection of survey data critical for developing instrument procedures. The webinar discussed standard workflow and submission processes, and clarifies NGS's role in reviewing data submissions.

NGS will switch to a vertical datum based on geopotential in just a few years. With that in mind, this webinar will describe “geopotential,” how it relates to gravity, and how NGS collects gravity data. Learn about relative vs. absolute gravity, terrestrial vs. airborne gravity, gravity vs. gravity gradient, and more.

NGS is developing OPUS-Projects so that GNSS vectors, including from real-time kinematic (RTK) surveys, can be uploaded to a survey network for least squares adjustment and submittal to NGS for publication. This has required developing a standardized GNSS vector exchange format known as GVX

This webinar provided an update on the GPSonBM program, including progress on the 2022 Transformation Tool Campaign and upgrades to the web map application and the underlying priority mark algorithm, as well as a new and exciting online Mark Recovery Form.

Presentation recognizes the improvements to Geoid18 and thanks users for participating in the GPS on BM campaign. The GPS on BM Campaign has been continued to emphasize its benefits in Vertical Datum Transformation and shows users how they can contribute data and how to use the GPS on BM Web Map to select specific priority bench marks.

NAVD88 and NAD83, which are still the official vertical and horizontal datums of the National Spatial Reference System (NSRS), have been identified as having shortcomings that are best addressed through defining new horizontal and vertical datums. The new reference frames (geopotential and geometric) will rely primarily on Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS) as well as an updated and time-tracked geoid model. This paradigm will be easier and more cost-effective to maintain. Learn how the new datums may affect your work. There are several specific actions to prepare for the release of the new datums in 2022. Suggested actions include: State Law Review and Modifications; State Plane Coordinate Impacts; Low Distortion Projections proposal; Improve current Geoid Models and Future Transformations by Observations on Existing Horizontal and Vertical Marks; and Additional CORS as part of National CORS.

The session will start with an overview of the many Products and Services that NGS provides to the geospatial community and will move into a discussion of NSRS Modernization, which is the blanket term for our forthcoming new datums and other improvements to our Nation's geodetic infrastructure. For those that have not already heard, NATRF2022 will replace NAD83, NAPGD2022 will replace NAVD88, and SPCS2022 will replace SPCS83. Specific details such as: what will be different about the geometric Reference Frame as compared to NAD83, what it means to be working in a Geopotential Datum, new terminology that will be used in the modernized system, the deprecation of the US Survey Foot, and some ways to prepare will be presented. This same session was presented on Thursday (13 February) afternoon and Saturday (15 February) morning.

This session will be a good follow-up to anyone who attends the Overview session on NSRS Modernization Thursday afternoon. We will discuss details on geoid models and computations, OPUS Static, OPUS Rapid Static, OPUS Projects, working in datum epochs, and some other general geodesy. Live demonstrations of the NGS Coordinate Conversion and Transformation Tool (NCAT), the NOAA VDatum application, and other online tools will be performed. A walk-through of OPUS Projects will be demonstrated, to better inform surveyors of its capabilities.

How NGS uses GPSonBM data to improve local accuracy of national scale products such GEOID18 and the 2022 Transformation Tool. How stakeholders can participate in sharing data and how they can prepare for NSRS Modernization.

The update to OMB Circular A-16 and official guidance on the implementation of the Geospatial Data Act (GDA) of 2018 is still pending and is expected to be released soon. As we wait for authoritative information on the way forward for federal coordination of geospatial data, please reserve time on your calendars on January 10 from 1:00 - 3:00 EST to join me and others for an update on the latest developments pertaining to the GDA and National Spatial Reference System (NSRS) Modernization effort.

The National Geodetic Survey is part of a broader effort in the global Positioning, Navigation, and Timing (PNT) community. In particular, NGS defines, maintains and provides access to the National Spatial Reference System (NSRS). As you can see in this simple opening paragraph, the acronyms are starting to pile up. There are a great deal of other groups with whom NGS works. This presentation will define and provide context for at least some of those groups. Participants should come away with a better understanding of what some of the acronyms mean. They should also get a better feel for how NGS activities tie into efforts to improve positioning in all Nations.

An era will soon end. In 1959, the name “U.S. survey foot” was given to an existing definition so that its use could temporarily continue alongside the new “international foot.” After December 31, 2022, only the international foot definition will be used in the United States: 1 foot = 0.3048 meter exactly (but simply called the “foot”). That will stop the simultaneous use of two nearly identical foot versions that differ by only 0.01 foot per mile. NGS and the National Institute of Standards and Technology have collaborated to resolve the problem of two feet, as described in this webinar by: * Giving an overview of the history * Providing examples of problems encountered * Summarizing public comments received * Charting a path forward as part of modernizing the National Spatial Reference System The intent is to provide national uniformity of length measurement in an orderly fashion with minimum disruption. It will end a dilemma that has persisted for over 60 years.

The United States will be updating the National Spatial Reference System in 2022. There will be four separate terrestrial reference frames all tied to the International Terrestrial Reference Frame. All will be identical to the ITRF at epoch 2022.0, but they will rotate according to Euler Pole Parameters determined for each of the four plates: North America, the Caribbean, the Pacific and the Mariana. While these EPP will describe most motion in these plates, significant horizontal and all vertical motions must be captured by deformation models or Intra-Frame Velocity Models (IFVM). These IFVM will likely derive from a single model based on a densified ITRF. However, these must each account for the EPP for each plate, leaving the relative motions to describe expected deformation throughout the four regional TRF's. How to develop these IFVM's is the focus of much research at the NGS. The simplest solution is simply to grid velocities at the nearly 2000 CORS. The recently completed reprocessing of CORS data has determined velocities for over 20 years. This velocity information works well in densely packed regions of CORS but performs below desired tolerance in sparsely covered regions. A denser grid may be obtained by using supplemental sites from private networks not included in CORS. This works better but uncertainty in the quality of some sites may affect the velocities. More complicated still would be incorporating geophysical models to better interpolate between control CORS. Finally, the use of satellite based InSAR would provide a basis for persistent updates. While InSAR may help in very remote regions such as the Mariana Islands, this can be problematic in North-South trending valleys between mountains, such as are found in the Rocky Mountains. Hence, it is likely that the optimal solution will be a combination of the above.

A 50 minute presentation giving a short history of U.S. horizontal / geometric datums and the coming new datum in 2022. Also provides why it is necessary to move on from NAVD88 to NAPGD2022 and generally how that will be accomplished. Presentation provides update on several NGS products, including NCAT and the NGS GPS on BM project for the 2022 vertical transformation model.

In March of 2012, The U.S. and Canada agreed upon a common value for defining the vertical datum in North America. The Canadian Geodetic Survey and National Geodetic Survey both reviewed tide gauge information at 211 points scattered along the Atlantic, Gulf of Mexico and Pacific coastlines in both countries. Estimates of Mean Ocean Dynamic Topography were removed from the tide gauges to account for disturbing forces from the global "mean" sea level value (Foreman et al. 2004, Thompson-Demiriov 2006). The resulting geometric positions of the ocean surface were then estimated in geopotential numbers using the GEOID09 model - for the US solutions. The result was a mean geopotential value at all tide gauges of 62,636,856.88 n2/s2 with a standard deviation of about 1.43 m2/s2. This value was acceptable close to the values adopted by both the IAU and the IERS: 62,636,856.00 m2/s2. Hence, both Canada and the U.S. adopted this value. Mexico later agreed to use this value as well in order to define a common vertical datum for all of North America. In the intervening time, a great deal has changed. A significant amount of additional satellite Gravity is available from both GRACE and GOCE. Additionally, the NGS GRAV-D missions have completed nearly all coastal areas. The most recent xGEOID19 model is based on these data and provides a better basis for estimating the heights at the tide gauges. Since the datum value has already been agreed upon, the effort here will be to assess the implied MODT at the tide gauges to differentiate between local and global MSL.

We hope you already know that the National Spatial Reference System (NSRS) will change in 2022, including the State Plane Coordinate System (SPCS). What you may not know is that you can be a part of that change. This presentation provides guidance on making requests to NGS for design of SPCS2022 zones in a state, how a state can propose and submit its own designs, and the special case of zones in more than one state. Topics include:

• • Who can submit requests and proposals
• • How to complete the forms
• • When it all must be done
• • Requirements for zone designs (the "rules")

The reasons for the rules will also be discussed, to show how they promote good design practice and provide consistency for a nationwide system intended for the future—but one that is also more complex than its predecessors.

Presentation provides an introduction to geodetic control in the context of flood mapping, presents case studies that highlight the importance of well-defined heights, and outlines the expected impacts of a modernized vertical datum on flood maps and related products. Also discusses why it is important to capture and use the metadata records regarding heights and to pay attention to local knowledge of heights.

NGS's future geopotential datum requires a dynamic geoid model for determining heights with centimeter accuracy. Geoid change in Alaska is rapid and challenging to model. This webinar overviews NGS efforts to model present-day geoid change in Alaska and its plans to observe this change directly. It also highlights how the geoid has changed through the 20th century.

Presentation gave an update on the new U.S. datums being determined by the National Geodetic Survey for 2022, along with changes to the state plane coordinate system.

To meet the needs of the high-precision GNSS community, the National Geodetic Survey (NGS) has constructed an absolute antenna calibration facility which uses field measurements and actual GNSS satellite signals to determine antenna phase center patterns. A pan/tilt motor changes the orientation of the antenna under test, and signals are received at a wide range of angles. The phase center patterns will be publicly available and disseminated in both the ANTEX and NGS formats. We provide the observation models and strategy currently used to generate NGS absolute calibrations, and propose some future refinements. We also show examples of antenna calibrations from the NGS facility. These examples are compared to the NGS relative calibrations as well as absolute calibrations generated by other organizations.

The National Geodetic Survey has established a strategic goal of developing the capability to obtain second-order, class II (FGCS standards) orthometric heights using GPS combined with a high resolution geoid model. As a contribution toward that goal, we are working toward a 1 cm (1 sigma) geoid model for the conterminous United States. Numerous signals effect the geoid at and above the 1 cm level, and one of the most difficult to properly implement has been the consideration of the permanent tidal potential in geoid modeling. In creating G96SSS, it was necessary to determine which tide system each of the following data sets were referred to: terrestrial gravity measurements, ship gravity measurements, altimetrically derived gravity anomalies, digital terrain, and EGM96 coefficients. In some cases, the question was difficult to answer. It was our intention to produce G96SSS in the non-tidal system. From recent knowledge of the parameters of the best fitting global ellipsoid, we know that the G96SSS geoid contains undulations biased from the non-tidal system by 12.0 cm. That is, undulations in the non-tidal system may be obtained from the G96SSS model by removing 12.0 cm from G96SSS. The tide system of GEOID96 was, by definition, dependent on the tide system of the NAD 83 GPS measurements, since GEOID96 was designed solely to convert between NAD 83(86) GPS ellipsoid heights and NAVD 88 Helmert orthometric heights. The GPS measurements were reduced to the non-tidal system, so GEOID96 is also in that system. Finally, the comparison between GPS heights on leveled benchmarks and G96SSS yieled an estimate of the bias of NAVD 88 from global mean sea level. In this comparison, it was essential to know the tide systems of both GPS and G96SSS. With all data reduced to the non-tidal system, our current best estimate of the NAVD 88 bias is -31.4 cm, where the sense of the sign is that the NAVD 88 H=0 reference level is 31.4 cm below global mean sea level.

NOAA’s National Geodetic Survey (NGS) has recently developed an innovative new technique for computing the absolute slant delays to GPS signals, caused by the ionosphere. This method relies entirely on ambiguous carrier phase data, using both the orbital geometry and the spacing of NOAA’s Continuously Operating Reference Station (CORS) network of GPS receivers over the Conterminous USA (CONUS) to solve for delays in absolute space. Using this technique, a set of absolute slant delays between any given CORS receiver and GPS satellite at any epoch can be computed, and these delays then referred to GPS receivers anywhere in CONUS using simple interpolation methods. This eliminates the need for a grid of vertical delays, and all the associated errors that accompany the mapping of vertical delays into slant delays. This method was tested against a variety of GPS positioning software and currently performs at the 1 TECU (about 1 cycle on L1) level in absolute mode and at the 0.01 to 0.1 TECU level in double differenced mode. NGS plans to begin computing daily models of the ionosphere slant delays in fall 2004 and releasing them as an experimental product under the name ICON-1 (for Ionosphere over CONus, version 1). The data will be made freely available for post processing and testing applications. Future plans will be to increase the accuracy of the modeling, reduce the latency of the models and formalize the model as an official NOAA product.

National Geodetic Survey (NGS) Chief Geodesist, Dr. Dru Smith, was interviewed on Federal News Radio 1500AM on Friday, May 21, 2010 following a press release that announced the conclusion of an NGS-hosted Federal Geospatial Summit.

Preliminary Analysis of IGS Reprocessed Orbit and Polar Motion Estimates Jim Ray (Jim.Ray@noaa.gov) Jake Griffiths (Jake.Griffiths@noaa.gov) The Analysis Centers (ACs) of the International GNSS Service (IGS) are reanalyzing the history of global network GPS data collected since 1994 in a consistent way using the latest models and methodology. This is the first reprocessing by the IGS, but it is expected to be repeated in the future as further analysis and reference frame changes occur. All eight final-product ACs are participating, together with three other related groups. First partial results consisting of IGS combined weekly SINEX TRF and EOP combinations have been submitted to the IERS for ITRF2008. A snapshot of the available AC weekly SINEX files was used covering the reprocessed years 2000 through 2007 plus the IGS regular operational solutions for 2008 (from week 1460 onward). Meanwhile, the full reprocessing campaign will continue to completion by about the end of 2009 and will cover the period 1994 to present with long-term consistent, combined SINEX, orbit, and clock products. We have examined the reprocessed AC orbit and polar motion (PM) estimates from the 1024 days (or 1025 for differences) of results till the end of 2007. These parameters are linked since PM is sensed in the GPS modeling as a global diurnal sinusoidal motion of the terrestrial frame relative to the satellite frame. Any similar type errors in the orbital frame can bias the PM and PM rate estimates. For the orbits, each daily AC satellite ephemeris for each pair of consecutive days has been fit to the extended CODE orbit model, extrapolated to the mid-point epoch between the days, and the geocentric satellite position differences computed to give time series of orbit repeatabilities. Occasional data gaps have been filled by linear interpolation, FFT power spectra computed, and the spectra stacked over the full GPS constellation and lightly smoothed. Our analysis reveals considerable diversity among AC orbits. Several show broad semi-annual (probably related mostly to eclipsing) and fortnightly spectral peaks, as well as even harmonics of the GPS draconitic year (1.040 cpy) with varying amplitudes. High-frequency white noise floors can be detected in most AC orbit spectra, with an average sigma of 14 mm and larger. AC PM spectra mostly follow a power law with slope -4 for periods shorter than about 20 d, as expected, except in the few cases when ACs have applied tight day-to-day continuity constraints. Indications of high-frequency white noise are seen in some AC series. Day-boundary discontinuities computed using the AC PM rate estimates can provide a sensitive probe of the quality of the AC modeling, especially for the satellite orbit dynamics. Like the orbit discontinuities, we find the PM discontinuities vary greatly among the ACs. But most spectra of the PM discontinuities show peaks at the annual (broad) and the O1 tidal alias period of 14.19 d (narrow), in addition to odd (rather than even) harmonics of 1.040 cpy. Previously both even and odd harmonics of 1.040 cpy have been found in the spectra of station position time series.

FUTURE IMPROVEMENTS IN DETERMINATIONS OF EARTH ORIENTATION PARAMETERS J.R. Ray NOAA, National Geodetic Survey, Silver Spring, MD, USA The present accuracy of multi-technique combined estimates for Earth orientation parameters (EOPs) can be assessed using the ITRF2005 and other recent experience as a baseline. Both components of polar motion (PM) have daily accuracies of about 30 micro-as (about 1 mm equatorial rotation). GPS observations dominate PM combinations owing to a strong global tracking network and continuous data. VLBI and SLR are weaker due to sparse, non-uniform networks so their PM rotational information is largely exhausted to align their frames with GPS. DORIS PM results are much noisier. GPS daily PM-rates are accurate to about 150 micro-as per day but are subject to prominent systematic errors related to orbit modeling and other effects. Such errors are less obvious in the daily PM offsets. UT1 accuracy is more difficult to evaluate because only VLBI is able to observe it. (Nutation is similar and will not be discussed here.) For VLBI networks designed to monitor EOPs, the daily UT1 accuracy is usually between 4 and 10 micro-s (2 to 5 mm equatorial rotation), though it is sometimes worse. Specialized hour-long, single-baseline UT1 networks yield errors around 25 to 30 micro-s with major systematic errors. LOD measurements from GPS have high-frequency errors of about 4 micro-s after modeling time-varying biases by comparison with the best VLBI UT1 data. Together, both can be combined to yield significantly improved UT1/LOD estimates, though this is not yet done routinely by most EOP services. Stronger future VLBI and SLR contributions will depend largely on the deployment of more robust ground networks; prospects are uncertain and recent trends are mixed. GPS PM is unlikely to be improved much. But addition of data from new GNSSs, with different orbital characteristics, might expose presently undetected systematic errors. GPS LOD performance has hardly changed for more than a decade. But, again, new GNSSs could be important given the strong link with orbital dynamics. At this time it is impossible to foresee how large any future improvements might be. Interest is often expressed in subdaily EOP variations but the main need now is for an updated geophysical model for the diurnal and semidiurnal tidal bands. Mitigation of network-dependent and other biases in the hour-long, single-baseline VLBI UT1 data is also needed. Detection of residual subdaily non-tidal PM variations (in the sub-mm range) remains distant, but progress in monitoring subdaily non-tidal UT1 will be a challenging possibility.

The National Geodetic Survey (NGS), part of the National Oceanic and Atmospheric Administration (NOAA) is responsible for defining, maintaining and providing access to the National Spatial Reference System (NSRS) for the United States. The NSRS is the official system to which all civil federal mapping agencies should refer, and contains, amongst other things, the official vertical datum (NAVD 88), horizontal datum (NAD 83) and great lakes datum (IGLD 85). Although part of the United States NSRS, all three of these datums have been created through international partnerships across North America. Unfortunately, time has shown both the systematic errors existent within these datums, as well as the inherent weaknesses of relying exclusively on passive monuments to define and provide access to these datums. In recognition of these issues, the National Geodetic Survey has issued a “10 year plan�, available online, which outlines steps which will be taken to update NAD 83, NAVD 88 and IGLD 85 concurrently around the year 2018. The primary source of success will be in the refinement of the CORS network and the upcoming execution of the GRAV-D project (Gravity for the Re-definition of the American Vertical Datum). Conversations are ongoing with colleagues in Canada, Mexico, Central America and the Caribbean in order to coordinate all of these efforts across the entire continent. The largest changes expected to occur are the removal of over 2 meters of non-geocentricity in NAD 83; the removal of decimeters of bias and over a meter of tilt in NAVD 88; the addition of the ability to track motions (subsidence, tectonics, etc) in the datums; the removal of leveling as a tool for long-line height differencing; the use of a “best� geoid as the orthometric height reference surface; the addition of datum velocities (motions of the geometric frame origin and motions of the geoid); and the use of GNSS technology as the way to access both orthometric and dynamic heights in the vertical datum. This talk will outline the broad plan of action and invite further collaboration along these lines.

Status and Prospects for IGS Polar Motion Measurements Jim Ray (1), Remi Ferland (2) (1) U.S. NOAA/National Geodetic Survey, USA (2) Geodetic Survey Division, NRCan, Canada GNSS-based measurements of polar motion by the International GNSS Service (IGS) dominate modern multi-technique combinations. This can be attributed to a very strong global tracking network and continuous data. IGS Final polar motion coordinates have daily accuracies of about 30 micro-as (about 1 mm of equatorial rotation), or perhaps a bit better for the most recent results. The daily polar motion rate measurements have larger errors, about 160 micro-as/day, largely due to greater sensitivity to errors in the IERS model for subdaily EOP tidal variations. Orbit modeling errors also affect the polar motion rates and perhaps also the polar motion offsets at a subtle level. IGS Ultra-rapid products provide reduced latency and more frequent updates with only modestly increased errors.

The National Geodetic Survey (NGS) of the United States, in collaboration with the National Aeronautics and Space Administration (NASA) and the International Earth Rotation Service (IERS), recently conducted a site survey of four space geodesy techniques: Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), Doppler Orbitography and Radio-positioning Integrated by Satellite instrument (DORIS), and the Global Positioning System (GPS), collocated at the Goddard Geophysical and Astronomic Observatory (GGAO) in Greenbelt, MD. This survey sought to determine, at the highest levels of accuracy, the geometric vectors which connect multiple geodetic techniques at a terrestrial site where these techniques are located near to one another. Realization of the International Terrestrial Reference Frame (ITRF) is enhanced by combining and comparing different space geodetic techniques through local ties referred to as site surveys. Because these four techniques all contribute their own strengths to the determination of the ITRF, the quality of the connectivity between the techniques is a direct contributor to the accuracy of the ITRF itself. Site surveys of the GGAO space geodesy techniques have been carried out periodically in the past. The site survey carried out by the NGS allowed for an independent comparison against results from previously conducted site surveys. The ultimate goal of this site survey was to improve the overall accuracy of local ties between space geodesy techniques by employing the latest surveying technology, as well as re-engage NGS in the field of IERS site surveys. Results of the survey will be presented, as well as discussion of future surveys and possible collaborations with other international surveying teams to improve the overall connectivity of techniques used in defining the ITRF.

Status and Prospects for Combined GPS LOD and VLBI UT1 Measurements Ken Senior (1), Jan Kouba (2), Jim Ray (3) (1) U.S. Naval Research Laboratory, USA (2) Geodetic Survey Division, NRCan, Canada (3) U.S. NOAA/National Geodetic Survey, USA Our Kalman filter combines irregular VLBI UT1-UTC with daily GPS LOD by handling correlated GPS errors with a Gauss-Markov plus fortnightly sinusoid model added to the random walk excitation. Evaluated against (AAM + OAM), this filter gives the lowest residuals and highest correlations. Optimal UT1+LOD results exclude UT1 from all Intensives plus other VLBI sessions with formal errors >5 microsec. Rescaling VLBI formal errors is not fully effective for the heterogeneous VLBI data. GPS LOD esimates are more uniform, but biased; but properly modeled, the LOD residuals are ~4 microsec. Addition of GPS LOD significantly improves combined UT1 series. Prediction services could benefit further using the IGS Ultra-rapid LOD values reported four times daily with 15 hr delay.

Preparations for the 2nd IGS Reprocessing Campaign Jim Ray The Analysis Centers (ACs) of the International GNSS Service (IGS) are now completing their first collective reanalysis of the history of global network GPS data collected since 1994. A consistent set of the latest models and methodology is being used to generate GPS orbits, Earth orientation parameters (EOPs), station coordinate time series, and station and satellite clocks. These results have been contributed to the new ITRF2008 multi-technique terrestrial reference frame and EOP combination. Preparations will begin during 2010 for the next IGS reprocessing effort. Despite the major progress made in the first IGS reanalysis, further analysis improvements remain to be implemented. The list includes: add GLONASS as well as GPS observations; adopt a new reference frame based on ITRF2008; update the IGS antenna calibrations based on the first reprocessing results and other sources; use the new EGM2008 geopotential model with perhaps revised time-varying coefficients; implement a model for previously neglected higher-order ionospheric effects; consider the satellite dynamical effects of Earth albedo reflection and re-radiated thermal emissions; apply various refinements in modeling tropospheric delays; include station displacements due the S1 and S2 atmospheric pressure tides; use a new model for the subdaily EOP tidal variations, if available; reconsider the handling of EOP constraints and a prioris by ACs; incorporate all high-order relativistic effects; and revisit the treatment of all analysis constraints to remove as many as possible and to understand better the effects of those that remain. Other operational aspects need to be evaluated also, such as how best to treat non-tidal loading station displacements, whether to continue forming weekly SINEX solutions or to move instead to daily integrations, and more consistent and rigorous methods to combine AC solutions.

Results from the New IGS Time Scale Algorithm (version 2.0) Ken Senior (1), Jim Ray (2) (1) U.S. Naval Research Laboratory, USA (2) Geodetic Survey Division, NRCan, Canada Since 2004 the IGS Rapid and Final clock products have been aligned to a highly stable time scale derived from a weighted ensemble of clocks in the IGS network. The time scale is driven mostly by Hydrogen Maser ground clocks though the GPS satellite clocks also carry non-negligible weight, resulting in a time scale having a one-day frequency stability of about 1E-15. However, because of the relatively simple weighting scheme used in the time scale algorithm and because the scale is aligned to UTC by steering it to GPS Time the resulting stability beyond several days suffers. The authors present results of a new 2.0 version of the IGS time scale highlighting the improvements to the algorithm, new modeling considerations, as well as improved time scale stability.

STATUS OF IGS CORE PRODUCTS The core products of the IGS consist of global terrestrial frames, GNSS orbits, Earth rotation parameters (ERPs), and clocks. Three main product series are issued with varying latency, accuracy, and completeness: Ultra-rapids (predictions and observations) for real-time and near real-time applications; later Rapids for near-definitive results; and still later Finals for the most complete and accurate uses. The accuracies of all IGS products are heavily dominated by systematic errors. Beginning with the orbits, rotational errors greatly exceed random noise probably due to limitations of current once-per-rev empirical parameterizations and errors in the IERS subdaily tidal ERP model. These error components alias into longer-period effects, including draconitic harmonics, and then propagate into all other products. Having said that, however, it is nevertheless true that the accuracy and utility of IGS GNSS products exceed that of any other sources, usually by large amounts, for all but a handful of observables, UT1 and the terrestrial frame scale being probably the most notable exceptions. The overall IGS quality has steadily improved over time, though we are probably near an asymptotic level now. A key responsibility of the IGS must be to identify the residual error sources in its products, develop methods to mitigate them, and advise users how best to avoid misinterpretation of spurious effects. This becomes an ever more challenging task as both the product generation and usage progressively move toward fully automated and routine operations. The current status of IGS products will be reviewed and suggestions offered for some operational changes.

Dependence of IGS Products on the ITRF Datum J. Ray (1) P. Rebischung (2) R. Schmid (3) (1) NOAA/National Geodetic Survey, USA (2) Institut Geographique National, France (3) Technische Universitaet Muenchen, Germany Throughout its history of nearly two decades, the International GNSS Service (IGS) has attempted to align its products as closely as possible to the successive realizations of the International Terrestrial Reference Frame (ITRF). This has been disruptive for IGS users at times, especially during the 1990s when some radial ITRF datum definitions were adopted. During the past decade IGS impacts due to ITRF updates have been smaller and mostly been caused by random and systematic errors in the results from the contributing space geodetic techniques. As with all techniques, frame rotational orientations are purely conventional and so the IGS relies on the ITRF via a subset of reliable, globally distributed stations with no significant problems. As regards the origin, the IGS in principle could be self-reliant, or contributory, in determining a frame origin aligned to the long-term center of mass of the entire Earth system. In practice, however, GNSS-based results have been less reliable than those from satellite laser ranging (SLR) to LAGEOS. So the ITRF origin, based on SLR only, has been adopted historically. Until the transition from ITRF2005 to ITRF2008 there have sometimes been significant shifts associated with this practice as SLR results have evolved. However, the present stability of the ITRF origin may finally have reached the ~1 mm level, though that remains to be verified. In many respects, the IGS dependence on the ITRF scale is most subtle and problematic. In addition to an overall Helmert alignment of the IGS frame to match the ITRF scale (and other datum parameters), since 2006 the IGS calibration values for the GNSS satellite antenna z-offsets depend directly on the same ITRF scale (due to high correlations if the IGS frame scale is not fixed). We therefore face a non-linear situation to maintain full consistency between all IGS products and the ITRF scale: each IGS frame contribution to ITRF based on one set of antenna calibrations must be used, together with frames from other techniques, to determine an updated ITRF and new antenna calibrations, which are then no longer strictly consistent with the starting IGS frame. One can hope that the process will iteratively converge to a sufficient accuracy eventually. But potentially large shifts in the ITRF scale, such as the -0.94 ppb (about -6 mm in height) change from ITRF2005 to ITRF2008, are highly disruptive, much more so than the associated rotational or translational shifts. Only SLR and very long baseline interferometry (VLBI) have been considered reliable and accurate enough to be used for the ITRF scale. But experience and theoretical studies have shown that neither is accurate to better than about 1 ppb. Note in particular that the formal 2 ppb error of GM (which should probably be closer to 1 ppb based on recent results) fundamentally limits the possible SLR/VLBI scale agreement to no better. Consequently, the IGS strongly urges that the ITRF scale hereafter be fixed conventionally to the ITRF2008 scale indefinitely in the future until it is convincingly shown that VLBI and/or SLR can determine the ITRF scale within 0.5 ppb. If this is not done, the IGS may maintain its own frame aligned to the ITRF2008 scale in order to minimize operational disruptions.

Current Accuracy of Terrestrial Positions from Space Geodesy In the International System (SI) of units, length is specified in terms of a corresponding time interval via an adopted value for the speed of light. Moreover, the SI second can be realized more accurately than any other base unit. So, since all space geodetic positioning systems rely inherently on high-accuracy timing measurements, one might suppose that position determinations can be traced directly and accurately to the SI meter. In fact, such metrological assessments are very limited. This is mainly because it is not practical to materialize metrological standards over distances longer than about 1 km, for which the best GPS accuracies demonstrated have been about 0.3 mm RMS. Relating such highly localized accuracies to global measurements is extremely problematic, however, for many reasons. Generally, errors unrelated to thermal measurement noise processes grow rapidly as the spatial scale increases and quickly dominate. The classical metrics most often used as a substitute for true global geodetic accuracy are: 1) repeatability of a given parametric estimate to gauge internal precision; and 2) differences among independent techniques to estimate external relative accuracy. Clearly, repeatability can only set a lower limit to true absolute accuracy since systematic biases are normally undetectable by this method. External comparisons, even when feasible, may be skewed unfavorably if it is necessary to use intermediate measurements, which have their own errors (such as local ties to relate station coordinates among co-located observing systems). When direct external comparisons are possible (such as for polar motion), the results can be optimistic if systematic errors are not genuinely independent (such as relying on common data reduction and geophysical models). When one system is clearly superior to any others, it is especially difficult to estimate its accuracy in any reliable absolute sense. Despite the difficulties involved, accuracy assessments can be useful to guide technique improvements by identifying limiting errors and spurring efforts to better control them. This paper will review current accuracy estimates for some space geodetic positioning measures.

Using the Vermont CORS Network to Access the National Spatial Reference System In 2006, the Vermont Agency of Transportation began to install a network of Continuously Operating GNSS Reference Stations (CORS). Now, nearly four and a half years later the network is almost complete. The use of the VT network by positioning professionals has been steadily increasing, and it is anticipated that its use will begin to grow exponentially over the next couple of years. Topics covered in this webinar will include: • A brief description of the VT CORS network and how it fits into the National CORS Network • Current capabilities and usage of the network • A description of current methods and techniques of accessing the NSRS using the VT CORS • Future trends for accessing the NSRS

The On-line Positioning User Service (OPUS) is a National Geodetic Survey tool that provides you with a National Spatial Reference System coordinate via email in seconds using your own GPS data file. The OPUS BETA website offers several notable enhancements. OPUS-Projects is a new option providing tools to handle GPS projects involving several sites occupied over several days. OPUS-Projects includes project visualization and management tools, enhanced processing options, and "one click" publishing for an entire project. OPUS-S uses a new processing strategy. By including more CORS at various distances and more sophisticated geophysical models, this new strategy improves the reliability of the results without sacrificing flexibility. OPUS-RS also offers a new CORS selection strategy which improves reliability and expands the regions in which this is a viable processing option. Underlying these enhancements are new CORS coordinates derived from a recently completed global GNSS network solution. This solution provides improved coordinates for all included CORS that are consistent with recognized reference systems such as the ITRF2008. These and other new developments will be described.

The On-line Positioning User Service (OPUS) is a National Geodetic Survey tool that provides you with a National Spatial Reference System coordinate via email in seconds using your own GPS data file. The OPUS BETA website offers several notable enhancements. OPUS-Projects is a new option providing tools to handle GPS projects involving several sites occupied over several days. OPUS-Projects includes project visualization and management tools, enhanced processing options, and "one click" publishing for an entire project. OPUS-S uses a new processing strategy. By including more CORS at various distances and more sophisticated geophysical models, this new strategy improves the reliability of the results without sacrificing flexibility. OPUS-RS also offers a new CORS selection strategy which improves reliability and expands the regions in which this is a viable processing option. Underlying these enhancements are new CORS coordinates derived from a recently completed global GNSS network solution. This solution provides improved coordinates for all included CORS that are consistent with recognized reference systems such as the ITRF2008. These and other new developments will be described.

The On-line Positioning User Service (OPUS) is a National Geodetic Survey tool that provides you with a National Spatial Reference System coordinate via email in seconds using your own GPS data file. The OPUS BETA website offers several notable enhancements. OPUS-Projects is a new option providing tools to handle GPS projects involving several sites occupied over several days. OPUS-Projects includes project visualization and management tools, enhanced processing options, and "one click" publishing for an entire project. OPUS-S uses a new processing strategy. By including more CORS at various distances and more sophisticated geophysical models, this new strategy improves the reliability of the results without sacrificing flexibility. OPUS-RS also offers a new CORS selection strategy which improves reliability and expands the regions in which this is a viable processing option. Underlying these enhancements are new CORS coordinates derived from a recently completed global GNSS network solution. This solution provides improved coordinates for all included CORS that are consistent with recognized reference systems such as the ITRF2008. These and other new developments will be described.

The On-line Positioning User Service (OPUS) is a National Geodetic Survey tool that provides you with a National Spatial Reference System coordinate via email in seconds using your own GPS data file. Several notable enhancements are pending or in development. OPUS-Projects is a new option providing tools to handle GPS projects involving several sites occupied over several days. OPUS-Projects includes project visualization and management tools, enhanced processing options, and "one click" publishing for an entire project. OPUS-S uses a new processing strategy. By including more CORS at various distances and more sophisticated geophysical models, this new strategy improves the reliability of the results without sacrificing flexibility. OPUS-RS also offers a new CORS selection strategy which improves reliability and expands the regions in which this is a viable processing option. Underlying these enhancements are new CORS coordinates derived from a recently completed global GNSS network solution. This solution provides improved coordinates for all included CORS that are consistent with recognized reference systems such as the ITRF2000. These and other new developments will be described.

The On-line Positioning User Service (OPUS) is a National Geodetic Survey tool that provides you with a National Spatial Reference System coordinate via email in seconds using your own GPS data file. Several notable enhancements are pending or in development. OPUS-Projects is a new option providing tools to handle GPS projects involving several sites occupied over several days. OPUS-Projects includes project visualization and management tools, enhanced processing options, and "one click" publishing for an entire project. OPUS-S uses a new processing strategy. By including more CORS at various distances and more sophisticated geophysical models, this new strategy improves the reliability of the results without sacrificing flexibility. OPUS-RS also offers a new CORS selection strategy which improves reliability and expands the regions in which this is a viable processing option. Underlying these enhancements are new CORS coordinates derived from a recently completed global GNSS network solution. This solution provides improved coordinates for all included CORS that are consistent with recognized reference systems such as the ITRF2000. These and other new developments will be described.

This webinar focused on describing the forthcoming change in coordinates (position and velocities) for CORS sites from ITRF2000 epoch 1997.0 and NAD 83(CORS96)epoch 2002.0. The new coordinates will be available in NGSTRF08 epoch 2005.0 and NAD 83(2011) epoch 2010.0. The underlying datum for IGS08 is based on ITRF2008, but the positions are calibrated for the impending release of IGS08 (+igs08.atx). In this webinar, we will describe the: - methodology used to establish the new coordinates - magnitude of the coordinate changes - implications for post-processing applications outside of NGS.e.g. holding CORS with fixed positions and use of absolute (vs. relative) antenna calibrations - time-frame for the distribution of coordinates

The mission of NOAA's National Geodetic Survey is to define, maintain and provide access to the National Spatial Reference System (NSRS), including vertical control for measuring accurate elevations. Since 2000, NGS has been implementing an initiative to improve access to the vertical component of the NSRS through technologies like Global Navigation Satellite Systems (GNSS). The program has been implemented through a state-by-state approach funded by Congressional earmarks, but in 2006 NGS began a more comprehensive approach to ensure consistency across the nation was achieved. NGS also began investigating a new approach to defining the vertical datum through a high accuracy gravimetric geoid. Details can be found in the project plan, Gravity for the Re-definition of the American Vertical Datum (GRAV-D), and in the NGS 10-year plan. This workshop will describe how each of these programs have a role to play in improving the vertical reference frame of the United States.

Results from the New IGS Time Scale Algorithm Since 2004 the IGS Rapid and Final clock products have been aligned to a highly stable time scale derived from a weighted ensemble of clocks in the IGS network [Senior et al., 2003]. The time scale is driven mostly by Hydrogen Maser ground clocks though the GPS satellite clocks also carry non-negligible weight, resulting in a time scale having a one-day frequency stability of about 1E-15. However, because of the relatively simple weighting scheme used in the legacy time scale algorithm and because the scale is aligned to UTC by steering it to GPS Time the resulting stability over shorter intervals and beyond several days suffers. A new time scale algorithm (version 2.0) has been implemented to address these limitations. The algorithm has been evaluated to a subset of data in the IGS REPRO1 reprocessing campaign, presented here. Repro1 products are currently being re-aligned using this new timescale algorithm.

This program discusses the foundational elements of the National Spatial Reference System (NSRS), including: Fundamental geodetic concepts of horizontal and vertical datums such as NAD 83 and NAVD 88; reference ellipsoids and geoid models. Discussions will include the realization of the datums in the form of GPS High Accuracy Reference Networks (HARNs) and the international densification of the Continuously Operating Reference Stations (CORS) network and their impact on the design and implementation of local geodetic systems, release of a new national geoid model, enhancements to the On-Line Positioning User Service (OPUS) suite of programs, and the major elements of the NGS ten-year plan for modernization of NSRS.

The GRAV-D (Gravity for the Redefinition of the American Vertical Datum) Project of the U.S. National Geodetic Survey plans to collect airborne gravity data across the entire U.S. and its holdings over the next decade. The goal of the project is to create a gravimetric geoid model to use as the vertical datum for the U.S. by 2021. Airborne gravity survey work began more than two years ago, with Alaska as a high priority for new data collection. Data collection there is underway and will be ongoing for several more years, but two roughly 400 km x 400 km surveys have been completed: in 2008 (centered over Cook Inlet near Anchorage) and in 2009 (centered over the Interior, to the north of the Alaska Range and west of Fairbanks). The gravity data for both surveys was collected with a MicroG LaCoste TAGS system but each survey utilized a different aircraft and survey layout. The 2008 survey was flown at 35,000 ft with the NOAA Cessna Citation jet, with 10 km data line spacing and 60 km cross lines spacing. The 2009 survey was flown at 12,500 ft with the Naval Research Lab King Air (RC-12) turboprop, with 7.5 km data line spacing and 37.5 cross line spacing. The 2008 data reveal the > 20 km resolution gravity effects of all the near-trench features (from accretionary prism to volcanic arc) for a 400 km stretch of the active plate boundary. In comparison, the 2009 gravity data allow a slightly better resolution (>15 km) view of the distal deformation to the north of the Alaska Range. The free-air gravity disturbances for each survey were computed and then complete (terrain-corrected) Bouguer gravity anomalies were calculated with Gauss-Legendre Quadrature integration (von Frese, et al., 1999) using standard density assumptions. Topography used to calculate the corrections came from the freely-available GTOPO30 (USGS, online) and bathymetry from the Smith and Sandwell (1997) altimetry-derived data. Interpretations of the complete Bouguer gravity anomalies will be made in the context of the tectonic activity in southern Alaska.

The U.S. National Geodetic Survey’s mission is to define and maintain the spatial reference system of the United States. Official policy, adopted in 2008, calls for the definition a new national vertical datum based on a gravimetric geoid by 2018 and for its maintenance into the future. The project that will accomplish data collection and analysis tasks toward that goal is called GRAV-D (Gravity for the Redefinition of the American Vertical Datum). The project is underway to collect new airborne gravity data across the entire U.S. To date, GRAV-D has collected nearly 1 million sq km of high-altitude airborne gravity data at 12,500 ft to 35,000 ft. Data sets exist in Alaska, Puerto Rico and the Virgin Islands, and the coastal Gulf of Mexico from the Florida panhandle to the Mexican border. In support of the GRAV-D mission, information about the geologic setting of the data sets and geophysical interpretations of the gravity data are necessary. For instance, geodetic concerns about knowledge of an area’s density structure for completing geoid calculations within topography can be addressed with geophysical interpretation techniques. Here we examine GRAV-D data located in a tectonically and topographically complex area of the country near Anchorage, AK and Fairbanks, AK. We assess the contribution of information gained from gravity analysis techniques, combined with information from geologic studies, for geodetic application in the area.

The mission of NOAA's National Geodetic Survey (NGS) is to "define, maintain and provide access to the National Spatial Reference System" (NSRS). NAVD 88 (North American Vertical Datum of 1988) provides the vertical reference for the NSRS. Comparisons with the Gravity Recovery and Climate Experiment (GRACE) satellite gravity data have demonstrated significant problems with NAVD 88. As repairing NAVD 88 through a massive leveling effort is impractical, NGS has decided to establish a gravimetric geoid as the vertical reference. The linchpin in NGS's effort is the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) program, which will ultimately incorporate satellite, airborne and terrestrial gravity data to build the geoid accurate to 1-2 cm that the U.S. surveying public requests. The GRAV-D program has two thrusts. First, a "high resolution snapshot" one-time measurement campaign with dense spatial sampling but short temporal span would be used to repair and improve existing gravity holdings. This campaign would involve airborne gravity surveys conducted over coastal areas first and interior areas later for the entire US and its holdings. Second, a "low resolution movie" will monitor temporal changes to the gravity field by tracking low order and degree changes in GRACE gravity data (Gravity Recovery and Climate Experiment satellite) augmented with a recurring terrestrial survey in areas of most rapid temporal changes. This effort would involve time series of absolute and relative terrestrial gravity measurements at these areas to help update the geoid over time. Initial data collection supporting GRAV-D was completed in July 2008. An airborne survey based out of Anchorage, AK covered an area 500 x 400 km over Cook Inlet and Kachemak Bay in 24 flights and about 100 flight hours. Funding from the US Army Corps of Engineers has facilitated surveying along the Coast of the Gulf of Mexico during the fall and winter, and a region covering Puerto Rico and the Virgin Islands. We present our project plan and most recent results.

The mission of NOAA's National Geodetic Survey (NGS) is to "define, maintain and provide access to the National Spatial Reference System" (NSRS). NAVD 88 (North American Vertical Datum of 1988) provides the vertical reference for the NSRS. Comparisons with the Gravity Recovery and Climate Experiment (GRACE) satellite gravity data have demonstrated significant problems with NAVD 88. As repairing NAVD 88 through a massive leveling effort is impractical, NGS has decided to establish a gravimetric geoid as the vertical reference. The linchpin in NGS's effort is the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) program, which will ultimately incorporate satellite, airborne and terrestrial gravity data to build the geoid accurate to 1-2 cm that the U.S. surveying public requests. The GRAV-D program has two thrusts. First, a "high resolution snapshot" one-time measurement campaign with dense spatial sampling but short temporal span would be used to repair and improve existing gravity holdings. This campaign would involve airborne gravity surveys conducted over coastal areas first and interior areas later for the entire US and its holdings. Second, a "low resolution movie" will monitor temporal changes to the gravity field by tracking low order and degree changes in GRACE gravity data (Gravity Recovery and Climate Experiment satellite) augmented with a recurring terrestrial survey in areas of most rapid temporal changes. This effort would involve time series of absolute and relative terrestrial gravity measurements at these areas to help update the geoid over time. Initial data collection supporting GRAV-D was completed in July 2008. An airborne survey based out of Anchorage, AK covered an area 500 x 400 km over Cook Inlet and Kachemak Bay in 24 flights and about 100 flight hours. Funding from the US Army Corps of Engineers has facilitated surveying along the Coast of the Gulf of Mexico during the fall and winter, and a region covering Puerto Rico and the Virgin Islands. We present our project plan and most recent results.

This presentation gives a short overview of gravity in relation to geodesy, as well as the instruments, processing, and interpretation involved in conducting airborne gravity studies. The slides are meant for a general audience or non-geology undergraduate student level.

Starting in 2008, airborne observations were made by the National Geodetic Survey over the state of Alaska. These data have been refined into aerogravity for use in developing geoid height models to serve as a future vertical datum. While the collection over the state is far from complete, the data processed thus far demonstrate the expected changes brought about by a consistent and seamless aerogravity campaign as a part of the Gravity for the Redefinition of the American vertical Datum (GRAV-D) project. This work shop will cover aspects of the collection as well as the net change to the gravimetric geoid model for some regions of Alaska. This is not yet a complete look, since not all of the data have been collected yet. However, it should provide insight into what the final model will look and the expected reliability of a future Alaskan vertical datum.

Starting in 2008, airborne observations were made by the National Geodetic Survey over the state of Alaska. These data have been refined into aerogravity for use in developing geoid height models to serve as a future vertical datum. While the collection over the state is far from complete, the data processed thus far demonstrate the expected changes brought about by a consistent and seamless aerogravity campaign as a part of the Gravity for the Redefinition of the American vertical Datum (GRAV-D) project. This work shop will cover aspects of the collection as well as the net change to the gravimetric geoid model for some regions of Alaska. This is not yet a complete look, since not all of the data have been collected yet. However, it should provide insight into what the final model will look and the expected reliability of a future Alaskan vertical datum.

Starting in 2008, airborne observations were made by the National Geodetic Survey over the state of Alaska. These data have been refined into aerogravity for use in developing geoid height models to serve as a future vertical datum. While the collection over the state is far from complete, the data processed thus far demonstrate the expected changes brought about by a consistent and seamless aerogravity campaign as a part of the Gravity for the Redefinition of the American vertical Datum (GRAV-D) project. This work shop will cover aspects of the collection as well as the net change to the gravimetric geoid model for some regions of Alaska. This is not yet a complete look, since not all of the data have been collected yet. However, it should provide insight into what the final model will look and the expected reliability of a future Alaskan vertical datum.

The use of the Global Positioning System (GPS) for positioning and mapping has been steadily increasing since its introduction in the late 1980’s. In the last few years, the use of GPS has exploded, primarily due to the establishment of regional or state-wide CORS networks that provide real-time correction data. The Vermont Agency of Transportation (VTrans) is in the process of building such a network with its primary purpose to support accurate positioning and mapping along Vermont’s Interstate corridors and other major highways. CORS are geodetic quality GPS receivers and antennas that are permanently installed. These stations collect GPS data continuously, and transmit data via the Internet to a central server. At the server, the data is archived for future use, and made available for download by any user. The incoming data is also processed at the server to generate corrections which are made available over the Internet to users in real-time. The Vermont Network has been named VECTOR (Vermont Enhanced CORS and Transmission Of Real-time corrections) to emphasize the expanded range of products available. The VT CORS Network has provided significant benefit to VTrans users and the tax payers of VT, and supports a variety of different applications from a diverse user community outside of VTrans. The information in this report shows that the direct savings VTrans has realized will likely pay for the system by the end of 2009, indicating a three-year return on investment. When considering the total savings realized by all users, the system paid for itself many times over in 2008 alone.

A presentation showing the current status of the vertical network in New England, and highlighting the need to modernize. The presentation discusses the rational for modernizing as discussed in the 10-year plan.

Presentation given to NGS employees and stakeholders at the 2010 NGS Convocation in Silver Spring, MD. The presentation goes over the NGS County Scorecard web survey results from a 2010 survey of over 500 members of the National Association of County Engineers or NACE. An overview is given of the current NGS Government Performance and Results Act or GPRA performance measure that includes the County Scorecard web survey as well as plans for a new replacement GPRA measure which tracks the progress of NGS' Gravity for the Redefinition of the American Vertical Datum (GRAV-D) initiative.

This is a .wav file of the NGS Director's opening remarks to congressional staffers and stakeholders during the rollout to Congress of a 2009 socio-economic benefits study of the NSRS, CORS and GRAV-D components. The full study is available here: http://www.ngs.noaa.gov/PUBS_LIB/Socio-EconomicBenefitsofCORSandGRAV-D.pdf A one page overview of the study is available here: http://www.ngs.noaa.gov/INFO/OnePagers/socio_eco_handout.pdf

This presentation is from the the keynote speech given by the NGS Director at the 2009 ESRI Survey & Engineering GIS Summit. Discusses the history, importance and future of the National Spatial Reference System (NSRS).

Brief NGS 101 and overview given by the NGS Director to new Hydrographic Services Review Panel (HSRP) members

Acting NGS Director, Ronnie Taylor, presents an update of Federal Geodetic Control Subcommittee(FGCS)activities to the Federal Geographic Data Committee (FGDC). FGCS website is: http://www.fgdc.gov/participation/working-groups-subcommittees/fgcs

Acting NGS Director, Ronnie Taylor, presentation to the Transportation Research Board 90th Annual Meeting. Provided an update on NGS activities including: new geopotential and vertical datums efforts, VDatum,GRAV-D, OPUS, LOCUS, Height Modernization, and Aeronautical Survey Program.

Acting NGS Director, Ronnie Taylor, update on NGS activities and 2010 accomplishments to the HSRP, including: Top 2010 Accomplishments, CORS, Shoreline Mapping, VDatum, County Scorecard, FY 2011 President's Budget and planned 2011 milestones.

NGS Director, Juliana Blackwell, provides an update to the HSRP on NGS activities including FY2010 performance measures, shoreline mapping ARRA funding, VDatum, Height Modernization, GRAV-D, Haiti earthquake response, Deepwater Horizon response, NGS 2010 milestones, FY2011 President's Budget and the Federal Geospatial Summit.

The California advisor and newly-appointed SW Region advisor will give updates on some of NGS' more popular programs, including the CORS network, OPUS, and DSWorld software. In response to requests, a review of the Datasheet fields and clarification of textual metadata will be provided. In light of increasing concerns about planning for Sea Level Rise, there will be a brief primer on tidal datums and usage of VDATUM software, which incorporates geodetic datums. Looking to the future, we will discuss the adoption of ITRF2008 for CORS coordinates, the shift to absolute antenna calibrations, and the migration-- in a decade or so-- to completely new horizontal and vertical datums.

The California advisor will give updates on some of NGS' tools and programs, including OPUS (data submission), as well as visualization tools such as DSWorld software and the Advisor's mapping website. A review of the Datasheet fields and clarification of textual metadata will be provided. In light of increasing concerns about planning for Sea Level Rise, there will be a brief primer on tidal datums and usage of VDATUM software, which incorporates geodetic datums. You will be informed about proposed changes in geodetic reference systems-- the adoption of ITRF2008 and the shift to absolute antenna calibrations impacting CORS coordinates this Spring, and the migration in a decade or so to completely new horizontal and vertical datums.

"Survey of the Coast", a predecessor of the National Ocean Service within the National Oceanic and Atmospheric Administration, is the oldest American civilian scientific agency established in 1807, to survey and map the nation's coastline. This organization also became the first agency to collect masses of geographic information (geodetic control, tidal, shoreline, soundings, geomagnetic, etc.) and processed this information to produce products for the safety and welfare of our citizens. Today the National Geodetic Survey continues to provide products and standards, including the national shoreline and derivatives including ortho imagery, processed lidar, and FGDC metadata to meet our nation's economic, social, and environmental needs. The National Geodetic Survey also provides emergency response imagery and lidar to support homeland security and emergency response requirements. The data is available through GeoSpatial One Stop, Digital Coast, and NOAA Shoreline Data Explorer applications.

NOAA's National Geodetic Survey (NGS) is mandated to map the National Shoreline, the legally-recognized shoreline depicted on NOAA nautical charts. While the primary application of this shoreline is in support of safe navigation, the data are now being used for an increasingly wide range of coastal science applications, including understanding and responding to threats of climate change. Over the past decade, NGS has collaborated with academic, government, and private sector partners to develop and implement new lidar-based shoreline mapping procedures. However, while NGS' lidar shoreline mapping workflow is now beginning to be used operationally, rigorous methods of assessing the uncertainty in the lidar-derived shoreline position have lagged behind in development. The study presented here aims to address this issue through development and comparison of two new methods of assessing uncertainty in NOAA lidar-derived shoreline...

NGS Director, Juliana Blackwell, provides an update to the HSRP on NGS activities including FY2011 and FY2012 information on performance measures, significant activities, milestones and budget.

IGS08: Elaboration, consequences and maintenance of the IGS realization of ITRF2008 The International GNSS Service (IGS) has designated its own realization of ITRF2008, known as IGS08, as the basis of its products starting in early 2011 and for the next full reprocessing campaign. The philosophy generally follows IGS practice since 2000 when the IGS97 realization of ITRF97 was adopted. However, unlike frames IGS97 through IGS05, IGS08 was initially intended to be a direct subset of well performing, stable GNSS stations from ITRF2008 rather than a separate GNSS-only frame solution. But, while the IGS contribution to ITRF2008 was computed using the original set of “absolute� GNSS antenna calibrations (igs05.atx), IGS08 had to be consistent with the latest set of calibrations (igs08.atx) that includes new determinations for some existing antennas. Coordinate corrections due to the antenna calibration updates were thus estimated and applied when possible to the ITRF2008 coordinates of 64 affected stations (out of a total of 232 stations in IGS08). As regards GNSS, the scale of the terrestrial frame is highly correlated with the satellite phase center offsets (PCOs) in the radial Earth direction. As the ITRF2008 scale differs by about -1 ppb from ITRF2005, new satellite PCOs consistent with ITRF2008 and IGS08 had to be derived for igs08.atx. They were obtained by back-solving the reprocessed solutions of five IGS analysis centers, while fixing their scales to the ITRF2008 scale. In order to satisfy regional users, many reference stations were selected in areas with dense GNSS coverage, such as Europe. This led to density heterogeneities in the IGS08 network, which is not optimal for the alignment of global frames. So a smaller, well distributed core network was additionally defined and recommended for global applications (such as for the IGS core products). Simulations show that using this core network instead of the full IGS08 set as reference frame indeed significantly reduces the “network effect�. Transformation parameters from IGS05 to IGS08 are unsurprisingly close to those from ITRF2005 to ITRF2008. Rotations are at the level of 0.01 mas so that the IGS orbits and Earth orientation parameters should be marginally affected by the switch from IGS05 to IGS08. But the scale difference of ~ -1 ppb and the Z translation of ~6 mm will result in changes in station positions by several millimeters. IGS08 is already beginning to suffer from continuous loss of reference stations due to earthquakes and mainly antenna changes, as was an even more critical problem for IGS05. To avoid a future crisis situation for the IGS products, it might be necessary to consider regular updates of the IGS08 reference frame before the next ITRF release. Such updates would require updated, post-discontinuity IGS08 coordinates to be estimated. A method to obtain such updated reference coordinates, based on the IGS operational cumulative solution, will be proposed.

Status of IGS Orbit Modeling and Areas for Improvement J.R. Ray (jim.ray@noaa.gov) J. Griffiths (jake.griffiths@noaa.gov) NOAA/NGS, Silver Spring, Maryland, US While the overall mean inaccuracy of the recent Final orbits of the International GNSS Service (IGS) is estimated to be about 2 cm (1D RMS), three aspects of the orbit modeling can probably be significantly improved: 1) ensure consistent and accurate modeling of satellite attitude variations; 2) mitigate spurious rotations of the constellations; and 3) add accelerations due to Earth radiation pressure. The errors associated with these are all highly systematic, not random. Reliable models for the attitude control of the older GPS satellites have been published for some years. Recently new models have been developed for GLONASS and the newest generation of GPS satellites as well. However, the implementation of these models among IGS Analysis Centers (ACs) is not consistent. Partly this is probably because the GPS Block IIR spacecraft were designed in such a way that attitude effects were nearly benign, so the major analysis errors were for the older, dwindling generations. However, with newer constellations and GPS Blocks the attitude variations probably cannot be treated so simply for high-accuracy results. The impact on user products is mostly on satellite clock variations and therefore on precise point positioning (PPP) results. So it is vital to ensure overall consistency by the IGS ACs adopting common models to generate combined products and by users implementing the same models in their PPP solutions. A leading error in the current IGS orbits is spurious net rotations of the constellation. It was learned in the early years of the IGS that once-per-revolution empirical parameters (or similar) were needed to model subdaily effects of solar radiation pressure. Failing to do so caused mainly large translational offsets in the Y component of the GPS orbit origin. But even with the higher-order parameterizations, much smaller rotational errors remain. The spectral features of these seem strongest near odd multiples of the GPS draconitic frequency (1.04 cycles per year) and probably also near fortnightly periods. Deficiencies in the widespread once-per-rev empirical modeling are likely to be responsible for these rotational errors. Most IGS ACs neglect the satellite accelerations due to reflected and thermally emitted radiation from the Earth as well as recoil thrust from the GNSS transmitters, largely because an accepted model for GNSS spacecraft is not yet available. Studies indicate that including at least the Earth albedo effect could remove most of the observed 2 cm bias between IGS orbits and satellite laser ranging. So developing an acceptable model and implementing it should be a high near-term priority for the IGS.

NGS Geodetic Tool Kit; a 2-hour Seminar The NGS Geodetic Tool Kit includes several geodetic computational utilities including the geoid computation utilities, HTDP, LVL_DH, the geodetic inverse and forward utilities, OPUS, gravity prediction utilities, NADCON, VERTCON, and the XYZ to latitude, longitude, height conversion utility. Some utilities you use every day and some you don’t. You probably don’t need to compute a geodetic inverse very often, or convert from geocentric coordinates X, Y, and Z to latitude, longitude, and ellipsoid heights on a daily basis, so you probably don’t have these utilities on your personal computer. But, when you need them they can be found in the NGS Geodetic Tool Kit! This workshop will highlight many of these utilities and describe their expected output and usage.

On-line Positioning User Service (OPUS); a 2-hour Seminar The National Geodetic Survey (NGS) operates the On-line Positioning User Service (OPUS) as a means to provide GPS users easier access to the National Spatial Reference System (NSRS). OPUS allows users to submit their GPS data files to NGS, where the data will be processed to determine a position using NGS computers and software. The position for your data will be reported back to you via e-mail in both the International Terrestrial Reference Frame (ITRF) and NAD83 coordinates as well as Universal Transverse Mercator (UTM), U.S. National Grid (USNG) and State Plane Coordinates (SPC) northing and easting. Recent and proposed developments regarding the various OPUS utilities will be discussed.

GPS-Derived Heights ; a 4-hour Seminar GPS-Derived Heights is a 1/2-day seminar detailing heights, height systems, their relationships, and development through the use of the Global Positioning System (GPS). Discussion describes the use of NGS GPS-Derived Ellipsoid and Orthometric Heights Guidelines. Development of sample projects and analysis of example baseline processing and project adjustments illustrate the basic concepts outlined. This seminar addresses both large scale and "local" projects, the use of the Continuously Operating ReferenceStations (CORS), On-line Positioning User Service (OPUS) and other NGS products and services.

Geodetic control is one of seven core framework themes in the California Geospatial Framework Data Plan document. Discussions are underway within a Work Group under the auspices of the CA GIS Council with regard to what type of geodetic control should be considered 'framework' points, who in California would be the steward for maintenance, and whether and how to incorporate real-time data into this theme. National Geodetic Survey has been responsible for providing an accurate National Spatial Reference System and the NGS Geodetic Advisor for California, an active member of the Work Group, will provide updates on the process of defining, populating, and maintaining the geodetic control framework layer in this state that has very active Earth surface processes, both horizontally and vertically.

This presentation provided information about NGS accomplishments in the past year and near-term future activities and was organized into 3 sections. 1)Priority programs: CORS, OPUS, GRAV-D with a subsection on GEOID09 in CA and OPUS-DB, and Ht Mod; 2)Updates of activities in many of the branches within the 6 Divisions; and 3)NGS as part of NOAA, particularly collaboration with CO-OPS.

A review of GPS and GRACE estimates of surface mass loading effects Tonie van Dam, Xavier Collilieux, Zuheir Altamimi, and Jim Ray Since its launch in 2002, many authors have compared GPS height coordinate residuals with radial displacements predicted from the Gravity Recovery and Climate Experiment (GRACE). Most comparisons have demonstrated significant annual correlations at perhaps 50% - 75% of the sites. At the other sites, there exists little to no correlation between the GPS observed and GRACE predicted heights. The disagreement is often attributed to problems in the GPS data analysis, e.g. ocean tide aliasing, seasonal monument motion, or reference frame effects. In this presentation, we revisit the GPS/GRACE comparison using GPS height residuals, GRACE data, and an environmental loading model in an attempt to better explain the discrepancy between the signals. We will also compare the degree-1 in the GPS time series with that from the environmental loading model.

Abs. To access the quality of NGS airborne gravity system and the impact of the flight altitude, NGS performed test flights at 1700, 6300 and 11000 meters altitudes in 2008, with track spacing 10 km for the two lower flights and 5 km for the highest flight. The flights provide not only important data sets for testing the precision and accuracy of the NGS airborne gravity system, but also the impact of the flight altitude to the collected gravity field. Results show that the system is stable and delivers high quality gravity data at three altitudes. The gravity collected at three altitudes agrees with each other from 1.4 to 3.3 mGal (RMS) at 11000 m flight altitude. If the biases are removed, the agreement is better than 1 mGal. At the ground, the downward continued gravity anomalies from the three altitudes agree within 1.9 to 3.8 mGal (RMS). After the biases removed, the agreement is better than 1.7 mGal. The similar results are obtained in comparison with NGS2008 surface gravity. The overall agreement between the downward continued airborne gravity at three altitudes and the NGS2008 surface gravity are better than 1.7 mGal, after the mean values are removed. The flight altitude has a direct impact on the airborne gravity accuracy. The comparisons show that the gravity collected at 11000 m altitude performance the worst, probably due to smaller signal/noise ratio and larger downward continuation effect. Due to 10 km track spacing, the gravity collected at 1700 m altitude does not outperform those collected at 6700 m altitude. Gravity at these two altitudes estimated to have an accuracy ±2 mGals at the ground.

The United Sates adopted the North American Vertical Datum of 1988 (NAVD 88) for its official vertical datum in the 1990s. Canada has been using the Canadian Geodetic Vertical Datum (CGVD28) for its height applications since the 1930s. The use of the different datums causes inconsistent heights across the border between the two countries, and the topographic height data from the two countries are not compatible. Both datums rely on passive control and significant pre-modern survey data, yielding not only misalignment of the datums to the best known global geoid at approximately 1-2 meters, but also local uplift and subsidence issues which may significantly exceed 1-2 meters in extreme cases. Today, the GNSS provides the geometric (ellipsoidal) height to an accuracy of 1-2 centimeters globally. Because of this, users have begun to demand a physical height system that is closely related to the Earth’s gravity field to a comparable accuracy. To address this need, government agencies of both countries are preparing the next generation of vertical datums. Even if the new datums are based on the same concepts and parameters, it is possible to have inconsistent heights along the borders due to the differences in the realization of the datums. To avoid inconsistency, it is in the interest of both countries to have a united, seamless, highly accurate vertical datum. The proposed replacements for CGVD28 and NAVD88 shall be based on GNSS positioning and a high accuracy gravimetric geoid that covers the territories of the United States, Canada, Mexico and the surrounding waters (to include all of Alaska, Hawaii, the Caribbean and Central America). To account for the effect of the sea level change, postglacial rebound, earthquakes and subsidence, this datum will also provide information on these changes. Detailed description of the definition, realization and maintenance of the datum is proposed. The challenges in realization and maintaining the datum are also discussed.

The geoid over the US Rocky Mountains is computed using two different procedures. The NGS group bases its geoid computations on Helmerts 2nd condensation method and presents an approximate and a precise version of it. The former is based on the Faye anomaly, which involves approximations of the terrain effect and the downward continuation of the surface gravity residuals to the geoid. The precise version is based on accurate account of the topographic masses and downward continuation. The second procedure leans upon the European geoid modeling; it uses the Molodenskii theory and converts height anomalies to geoid heights. Both procedures employ EGM08 as a reference field and SRTM-DTED1 (3") elevations. However, the two procedures use different maximal degrees of EGM08 and utilize its low degrees differently. The results are compared to GPS Bench Marks and the resulting deflection models to astro-geodetic deflections.

The biggest obstacle in solving the geodetic interior boundary value problem is the unavailability of the mass density distribution of the Earth. However, if the density of the topography is known, solutions valid only in the topographic masses can always be found after some mathematical manipulations. The disturbing potential inside the topographic masses is “harmonized� by subtracting a non-harmonic potential field. The “harmonized� potential field is then solved by analytical downward continuation. A solution for the non-harmonic potential is presented for the special case where the mass density of the topography is a constant.

Based on the assumption that the ultra-high frequencies of the gravity field are produced by the topography variations, we compute the omission errors by using 3 arc-second elevation data from the Shuttle Radar Topography Mission (SRTM). It is shown that the omission errors to the geoid are in the range of dm, cm and sub-cm level for grid sizes of 5', 2' and 1' over the contiguous United States (CONUS), respectively. The results suggest that a 1 arc-minute grid size is sufficient for the 1-cm geoid, even for areas with very rough topography and high gravity variations. The results also show that the omission errors to gravity are significant even for 1' grid size, at which the smoothed-out gravity still reaches tens of mGals. The omission errors to gravity at a 5' grid size peaks above 100mGals, demonstrating the importance of correction of residual terrain to gravity observations in data gridding or block mean value computations. The results are also compared with those based on Kaula’s rule. While the omission errors based on Kaula’s rule are 0.5 and 3.0cm for 1' and 5' grid size, respectively, the RMS values of the omission error in this paper are 0.1 and 1.1cm. The differences suggest Kaula’s rule may overestimate the power of the gravity field at the ultra-high frequency band, which renders the convergence studies of the spherical harmonic series based on Kaula’s rule questionable.

Since its official unveiling at the 2008 General Assembly of the European Geosciences Union, EGM2008 has demonstrated that high-degree harmonic expansions constitute a useful and effective final representation for high-resolution global gravitational models. However, such expansions also provide a versatile means of capturing (modeling), inter-comparing, and optimally combining local and regional high-resolution terrestrial data sets of different types. Here we present a general recipe for using high-degree expansions to capture, downward-continue and assimilate airborne survey data. This approach relies on the production of two ‘competing’ high-degree expansions. A first, ‘terrestrial-only’ expansion incorporates EGM2008 globally, and high-resolution terrestrial gravimetry regionally. This expansion can be used to upward-continue the regional terrestrial data to the flight level of the airborne survey, such that the terrestrial gravimetry outside the survey area can be merged with the airborne data inside the survey area, all at flight level. Harmonic analysis of this merged data set, also at flight level, yields a second ‘airborne-augmented’ expansion, which closely matches the ‘terrestrial-only’ expansion outside the survey area, but which also closely reproduces the airborne survey data inside the survey area. Capturing the airborne and terrestrial data in this way means that downward-continuation of the airborne data, as well as spectral/spatial comparison (and ultimate combination) of the airborne data with the terrestrial (and satellite) data, can all be achieved through spherical- and ellipsoidal-harmonic synthesis of these two competing expansions, and their spectral combination. This general approach is illustrated with a worked example.

The workshop will consists of: 1. General overview digital leveling - NGS way 2. WINDESC program - with hands on examples 3. Translev program - with hands on examples 4. LOCUS 5. Project reports. The goal is at the end of the 8 hours a small leveling project will be completed. Plus, the workshop will be alot on hands with examples and problems so everyone will need to have their own laptop.

A 2-hour seminar was webcast live and recorded to provide researchers and scientists working on the (San Francisco) South Bay Salt Pond Restoration Project with a clear understanding of geodetic vertical and tidal datums in the area. The following website includes links to the webinar as well as presentation materials and related reports from SSF Bay studies. http://www.southbayrestoration.org/science/2011-datums-seminar/

A 2-hour seminar was webcast live and recorded to provide researchers and scientists working on the (San Francisco) South Bay Salt Pond Restoration Project with a clear understanding of geodetic vertical and tidal datums in the area. The following website includes links to the webinar as well as presentation materials and related reports from SSF Bay studies. http://www.southbayrestoration.org/science/2011-datums-seminar/

Reference frame changing for CORS; Adjustment/Datum tag changing for passive; CORS what's different?; Want to keep up?; HTDP what's different?; RTN Guidelines; GC Mapping tools; Learning Resources

CBL Process CBL Site Characteristics Adoption of new reference frame for CORS Subsequent adjustment for passive stations HTDP CGAR Developments of various NGS products

The U.S. Army Corps of Engineers (USACE) National Oceanic and Atmospheric Administration (NOAA) and the Federal Emergency Management Agency (FEMA) are in the early stages of developing a tri-agency initiative entitled SAGE, which stands for Systems Approach to Geomorphic Engineering. The purpose of this tri-agency initiative is to pursue and advance a comprehensive view of shoreline change and to utilize integrated methodologies for coastal landscape transformation to slow/prevent/mitigate/adapt impacts to coastal communities from the consequences of climate change. This concept will utilize a holistic approach in exploring the idea of hybrid engineering, linking "soft" ecosystem-based approaches with "hard" infrastructure approaches, to develop innovative techniques and solutions to aid in the adaptation of our changing coastlines. This presentation is an overview of National Ocean Service (NOS) contributions to understanding essential integrated data needs for inporming SAGE. It was presented by Juliana Blackwell, Director of NOAA's National Geodetic Survey.

In North America, the last attempt to unify the vertical datum, the North American Vertical Datum of 1988 (NAVD88), was only adopted by the USA and Mexico, while Canada elected to remain on the Canadian Geodetic Vertical Datum of 1928. Furthermore, no attempt to provide a unified datum to the Central American and Caribbean nations was part of NAVD88. This has led to continued cross-border height issues on the continent. Recently, Canada and the United States have initiated policy decisions to replace their respective datums with new datums realized primarily through GNSS technology and a gravimetric geoid model. The USA has decided to wait until the GRAV-D campaign is complete (2022) to make this change. Canada will likely adopt sooner in 2013, with a possible update in 2022 aligned with the USA. Although Mexico has not yet adopted a policy of replacing NAVD88, they are participating in all coordinated efforts towards obtaining a common datum. Government geodetic agencies in the USA, Canada and Mexico are working toward the joint computation and adoption of a single gravimetric geoid model covering all of North America, including all parts of Alaska, Hawaii, Central America and the Caribbean. The adopted geoid model will be coordinated with (but may not be identical to) the IAG's adoption of a unified World Height System. The North American unified vertical datum will be accessible to all nations in this region through GNSS technology. This paper discusses progress toward the unification of a vertical datum for the entire continent.

We have developed a block model of tectonic deformation of North America west of longitude 100° W and between latitudes 30°N and 49°N. NOAA's National Geodetic Survey (NGS) is in the process of incorporating this model into version 3.1 of the horizontal time dependent positioning (HTDP) software tentatively scheduled for release in early 2011. By estimating the horizontal linear velocity for any point on the ground, HTDP enables surveyors and others to update (or backdate) positional coordinates measured on one date to corresponding coordinates that would have been measured on another date. The model consists of 59 crustal blocks with 46 independent rotation poles and 38 independent strain rate tensors. The model also includes elastic coupling coefficients on faults that bound adjacent blocks. NGS recently updated estimates for model parameters by using 6,063 GPS-derived velocity vectors (including vectors from the 2009 Plate Boundary Observatory (PBO) solution and the NGS Multiyear CORS) and 330 geological measurements of fault slip and/or fault orientation. In general, the fault slip rates and the interseismic coupling coefficients are consistent with the results of previous studies; however, because of the comprehensive nature of this model, we are able to quantitatively map deformation rates over the entire deforming region. Slip rates on the faults range from over 30 mm/yr for the Cascadia subduction zone and parts of the San Andreas system to near zero for faults adjacent to stable North America. In particular, our study confirms very low deformation rates across eastern Nevada and western Utah.

Are the National Geodetic Survey's surface gravity data sufficient for supporting a 1cm-accurate geoid? We evaluate the errors of these surface data and their effect on the geoid. Long wavelength errors are derived by comparison to synthetic GRACE gravity and high-frequency errors by crossover analysis and K-Nearest-Neighbor predictions.

Discussion of the new geometric and vertical datums NGS intends to deliver on or about 2012.

Heights (elevations) are complicated. Some are reckoned as straight lines perpendicular to a reference surface (ellipsoid heights), some are curved lines parallel to gravity at every point (orthometric heights), and some 'heights' have no geometric meaning at all yet tell you where water will go (dynamic heights). The datum to which heights refer can be a mathematical ellipsoid surface, which in turn is referenced to one of several different global or regional frames. It can be a vertical datum defined by a geodetic leveling network, or by a geoid, a gravitational equipotential surface more-or-less representing global mean sea level. It can be defined by a particular tide gage as local mean sea level, or mean high water, or mean lower low water, etc. Adding to the complexity, heights are measured by a wide variety of equipment, each with corrections, models, and methodologies that yield particular types of heights referenced to various datums over a broad range of accuracies. NOAA has created two tools, VDatum and LOCUS, to help geospatial professionals make better use of height data and measurements. VDatum is free software developed jointly by NOAAs National Geodetic Survey (NGS), Office of Coast Survey (OCS), and Center for Operational Oceanographic Products and Services (CO-OPS). It vertically transforms geospatial data among a variety of tidal, orthometric, dynamic, and ellipsoidal height systems. This allows users to convert their data from different vertical (and horizontal) references into a common system and enables the fusion of diverse geospatial data into a uniform reference system. For example, VDatum can be used to combine a bathymetric survey referenced to a local tidal datum with a digital elevation model based on the North American Vertical Datum of 1988 (NAVD 88) into a single seamless surface model. LOCUS (Leveling Online Calculations User Service) is a free Internet-based NGS service that checks, corrects, and adjusts leveling data submitted by users and provides heights with respect to published NGS vertical control. Philosophically, it is similar to the popular NGS Online Positioning User Service (OPUS) used for GPS data. As with OPUS, the intent is to make it as simple as possible for users to get correctly adjusted heights by uploading their leveling data via the Internet and immediately receiving results. For example, if a user wants to level with respect to NGS NAVD 88 benchmarks, LOCUS will apply the appropriate corrections (including the gravity model) to convert the observed leveled heights differences to NAVD 88 orthometric heights. Whether combining existing vertical datasets from a variety of sources (VDatum) or correcting and adjusting precise vertical measurements (LOCUS), NOAA has developed tools that will assist users in achieving great heights.

This presentation follows previous talks that focused on outreach and education of surveyors. It is designed to update surveyors on the latest research related to the development of geoid height models as tools for datum transformation between NAD 83 and NAVD 88. All previous geoid height models have relied upon control data existent in the National Geodetic Survey Integrated Database (NGSIDB) to develop the conversion surface between the datums. In GEOID09, nearly 20,000 such points were available. However, about half of these points were located in only four of the lower 48 states. Most of the nearly 500,000 bench marks that exist in the NGSIDB have never been occupied with a GPS receiver. Hence, the bulk of the points are unused in determining the conversion surface. Given the disparate distribution of the few points that were occupied with GPS and the desire to supplement these in sparsely covered regions, alternative control data is desirable. The Online Positioning User Service Database (OPUS-DB) is where surveyors have the option of storing their observations for the use of others. Many of these marks were obtained on leveled bench marks. In November of 2010, there were about 422 points pulled from OPUS-DB with 285 representing new bench marks and providing supplemental control not previously available. These points are spread across the country and provide significant improvement in many regions, especially the sparsely covered western states. The errors resulting from interpolation over hundreds of kilometers can result in dm to multi-dm level errors in the resulting geoid height model. The OPUS-DB determined points then supplement the existing coverage from the NGSIDB. Many of these gaps were filled, and this reduced the interpolation error for those regions. More over, a campaign can be put in place to identify the sparse regions and likely candidate bench marks to target and fill these gaps. State Advisers/Coordinators and various state surveying groups have begun to organize efforts to collect GPS observations on the previously unoccupied bench marks and store them in OPUS-DB. For example, the distribution of control data from the NGSIDB points in Arizona have been examined, and that State Adviser has made known regions that require supplemental information in the OPUS-DB. These points will be examined as they become available and a determination made as to whether to incorporate them into future geoid height models. Preliminary analysis does indicate that there is some slight inferiority to the quality of OPUS-DB data in that the apparent error signal (noise) is generally about double that of NGSIDB data. However, noisier data can be accounted for using least squares collocation - missing signal due to gaps cannot be easily overcome. Use of OPUS-DB to supplement coverage shows great promise as a means of readily collecting information without the need for following the Bluebook, but doing so where it can provide the most improvement to future geoid height models for datum transformations.

Extensive airborne gravity surveys have been conducted as a part of the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project by the U.S. National Geodetic Survey. The intent is to capture the mid-wavelengths of the gravity field over all of the U.S.A. GRAV-D bridges the gap between long wavelengths determined by satellite gravity missions and shorter wavelengths determined from surface observations as well as forward-modelling of surface density and elevation models. The GRAV-D surveys were collected in 10-km spaced profiles covering 400-500 km patches, which are adequate in scale to compare to Earth Gravity Models through about degree 90. Initial comparisons with EGM2008 revealed no detectable slope across these patches, supporting the idea that no significant long wavelength differences exist between the aerogravity and the GRACE satellite data on which EGM2008 is based. However, only half the signal in EGM2008 is from satellite data at degree 95; indicating that a strict comparison of GRAV-D to the GRACE gravity field is less than exact. With the release of the GOCE data, higher resolution EGM's based entirely upon satellite gravity models make this comparison a more direct assessment of the long to intermediate quality of the aerogravity. This will enable generation of an EGM with 20 km resolution (approximately degree 2000). In turn, this model will be combined with the existing terrestrial data to build a higher resolution model towards defining a cm-level accurate gravimetric geoid model to be used as a new vertical datum for the United States.

NOAA's National Geodetic Survey (NGS) is responsible for maintaining the National Spatial Reference System. This includes the national geometric and geopotential datums, which are the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88), respectively. For NAVD 88, Helmert orthometric heights were defined in a block adjustment of over 500,000 geopotential differences at bench marks. As an alternative to leveling from established bench marks, NGS provides geoid height models such as GEOID09 (Roman et al. 2011) that transform between NAD 83 and NAVD 88. This provides the ease of calculating your position with GPS but yields more practical orthometric heights. To develop such models requires that both the GPS-derived ellipsoidal and leveling-derived orthometric heights on Bench Marks (GPSBM's) be known. Because of the requirement for both heights on a bench mark, the pool of control points is much smaller (only about 18,000) and not very equitably distributed (with potential dm-level interpolation errors). This paucity of points is driven by the rigorous processes ("Bluebooking") required to enter data into the NGS Integrated Database (NGSIDB). To mitigate this, the Online Positioning User Service Database (OPUS-DB) was explored as a source for supplemental data. This nascent database is rapidly being accepted by the broader surveying community and can even be used to target significantly deficient areas. A pull of OPUS-DB in November 2010 yielded 422 points. While this number is small in comparison to the overall NGSIDB data, the potential for growth is significant. These points fell into three categories: (1) 80 that were common to both databases and were used in making GEOID09, (2) 57 that were common to both but not used in making GEOID09, and (3) 285 with new geometric observations for points not previously observed with GPS (i.e., new control points). Residual values were formed by removing the same geoid and orthometric heights from ellipsoid heights obtained from NGSIDB and OPUS-IDB. Smaller values imply a better fit and less noise. For the first group, OPUS-DB was noisier (SD 0.031 m (one sigma)) than NGSIDB (SD 0.015 m (one sigma)). For the second group, OPUS-DB was less noisy (0.037 m (one sigma)) than the NGSIDB (0.043 m (one sigma)). For the last group, only OPUS-DB data were available and they were a little worse (0.047 m (one sigma)) than before. This is consistent with the level of agreement seen when forming residuals between ellipsoidal heights from NGSIDB and OPUS-DB in groups 1 and 2 (SD of 0.028 m and 0.044 m (one sigma), respectively). Overall, OPUS-DB demonstrated very good agreement with more rigorously determined NGSIDB data, provided expanded coverage into regions with poor coverage, and demonstrated a significant potential for use in future geoid modeling.

COOL GEODETIC RESOURCES FOR YOUR PROJECT Nearly every effort that involves planning, protecting, or monitoring our Nation's coasts and Great Lakes relies on knowing or establishing geographic positions and elevations of objects or locations-of-interest in the project area. A recommended method to accomplish that is to reference the project to the well-known and respected reference system, the National Spatial Reference System (NSRS). The NSRS, defined and maintained by NOAA's National Geodetic Survey (NGS), is a consistent National coordinate system that specifies latitude, longitude, height, scale, gravity, and shoreline throughout the Nation. It is NGS' mission to develop and provide access to the NSRS "to meet our Nation's economic, social, and environmental needs." This panel discussion will improve attendees' knowledge of methods they can use to obtain and use geodetic control. It will also update the audience about NGS' goals for improving the definition and delivery of horizontal and vertical datums. This session will inform the audience about new methods developed by NGS to facilitate easy access to data for approximately 1.5 million geodetic control marks that exist in the NGS database, with a brief description of software tools such as DSWorld, which works with GoogleEarth. It will inform the audience about the latest Online Positioning User ServiceÂ? (OPUS) utilities, which can be used to establish, or check, coordinates and elevations for projects referenced to the NSRS, enabling users to complete their work more efficiently. Also to be covered will be information about resources that are available to anyone needing assistance with locating, using, or producing geodetic information about their projects. Attendees will learn about NGS' Geodetic Advisors, who are located around the United States with the purpose of educating and assisting people in utilizing NGS products and services in their projects or applications.

Nearly every effort that involves planning, protecting, or monitoring our Nation's coasts and Great Lakes relies on knowing or establishing geographic positions and elevations of objects or locations-of-interest in the project area. A recommended method to accomplish that is to reference the project to the well-known and respected reference system, the National Spatial Reference System (NSRS). The NSRS, defined and maintained by NOAA's National Geodetic Survey (NGS), is a consistent National coordinate system that specifies latitude, longitude, height, scale, gravity, and shoreline throughout the Nation. It is NGS' mission to develop and provide access to the NSRS "to meet our Nation's economic, social, and environmental needs." This panel discussion will improve attendees' knowledge of methods they can use to obtain and use geodetic control. It will also update the audience about NGS' goals for improving the definition and delivery of horizontal and vertical datums. This session will discuss the relationship of geodetic and tidal vertical datums, and the necessity of understanding how to describe the relationship. The software program VDATUM was developed jointly by NOAA's NGS, Office of Coast Survey (OCS), and Center for Operational Oceanographic Products and Services (CO-OPS) to enable users to easily transform data from various vertical and/or horizontal datums into another datum for a location that is on the tidally influenced coastline. The input data can be elevations or (bathymetric) soundings, and batch files can be submitted. A brief tutorial will illustrate how to use the software, the accuracy associated with the conversions, and some of the common errors that users make.

COOL GEODETIC RESOURCES FOR YOUR PROJECT Nearly every effort that involves planning, protecting, or monitoring our Nation's coasts and Great Lakes relies on knowing or establishing geographic positions and elevations of objects or locations-of-interest in the project area. A recommended method to accomplish that is to reference the project to the well-known and respected reference system, the National Spatial Reference System (NSRS). The NSRS, defined and maintained by NOAA's National Geodetic Survey (NGS), is a consistent National coordinate system that specifies latitude, longitude, height, scale, gravity, and shoreline throughout the Nation. It is NGS' mission to develop and provide access to the NSRS "to meet our Nation's economic, social, and environmental needs." This panel discussion will improve attendees' knowledge of methods they can use to obtain and use geodetic control. It will also update the audience about NGS' goals for improving the definition and delivery of horizontal and vertical datums. This session will provide information about the efforts underway to produce a new International Great Lakes Datum (IGLD), with a goal for release in 2015. Being discussed are the reasons why a new IGLD is desirable, the data collection and analysis effort to update the datum, and examples of the impact of the new datum on the Great Lakes region. The international GPS campaign related to the new IGLD, completed in the Great Lakes region in 2010 by Natural Resources Canada's Geodetic Survey Division and NOAA's NGS, will be described.

Global Navigation Satellite System (GNSS) data processing requires many different numerical models to describe the physical processes affecting the positions of the satellites and points on the ground as well as the propagation of the GNSS signals from the satellites to the user. Some of these models are commonly known: satellite orbits, tropo and antenna corrections are examples from this group. Others are probably less well known: phase wrapping, atmospheric gradients and solid Earth tides are examples from this group. In this presentation, many of these models will be described with a focus on broader conceptual understandings rather than detailed technical descriptions. Real examples from data processing will be included whenever possible thereby adding the magnitudes of these physical processes to your understanding. The ultimate goal is to give you a better awareness of what your GNSS processing software should be doing to give you the accuracy necessary for your needs.

The National Geodetic Survey, NGS, traces its history back to the early 1800's. Although its mission has adapted to changing times and technology, this two hundred year history is alive in the NGS today. Using an overview of the NGS as an organizing framework, some NGS activities of particular interest to the surveying communities will be highlighted. Among the activities highlighted in this presentation are: improved coordinates for the CORS and a large subset of the passive mark networks (NAD 83(2011) and NA2011); the related work to define a new hybrid geoid model providing improved consistency with these new coordinates and velocities (GEOID12); the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) mission to create a snapshot of gravity across the United States in unparalleled detail; the Online Positioning User Service (OPUS) providing virtually hands-off, high-accuracy GNSS data processing; and the creation of guidelines to help real-time network providers more rigorously tie their networks to the global and national datums.

The Online Positioning User Service (OPUS) is a National Geodetic Survey tool that provides you with a National Spatial Reference System coordinate via email in seconds using your own GPS data file. Several notable enhancements have been implemented or are pending for OPUS. OPUS-Projects is a new option providing tools to handle GPS projects involving several sites occupied over several days. OPUS-Projects includes project visualization and management tools, enhanced processing options, and one click publishing for an entire project. OPUS is testing a new static processing strategy. By including more CORS at various distances and more sophisticated geophysical models, this new strategy improves the reliability of the results without sacrificing flexibility. OPUS-RS also offers a new CORS selection strategy which improves reliability and expands the regions in which this is a viable processing option. Underlying these enhancements are new CORS coordinates derived from a recently completed global GNSS network solution. This solution provides improved coordinates for all included CORS that are consistent with recognized reference systems such as the ITRF2008. These and other new developments will be described.

The California Geodetic Advisor will discuss: NEW Coordinates and epoch for the NSRS CORS that were published on Sept 6; In-progress adjustment of nearly 80K passive stations nationwide; Development of GEOID12 based on new ellipsoid heights; Changes to the Datasheet format/content; and DSWorld: a GoogleEarth mapping tool and more.

The National Oceanic and Atmospheric Administration's (NOAA), National Geodetic Survey (NGS) has embarked on a ten year project called GRAV-D (Gravity for the Redefinition of the American Vertical Datum). The purpose of this project is to replace the current official vertical datum, NAVD 88 (the North American Vertical Datum of 1988) with a geopotential reference system based on a new survey of the gravity field and a gravimetric geoid.
As part of GRAV-D, NGS plans to execute a set of "geoid validation surveys" at various locations of the country. These will be surveys designed to independently measure the geoid to provide a check against both the data and theory used to create the final gravimetric geoid which will be used in the geopotential reference system.
The first of these surveys, known as the Geoid Slope Validation Survey of 2011 (GSVS11) was executed between July and October, 2011 in the central region of Texas. The survey took place over a 325 kilometer line running more or less north-south from Austin to Corpus Christi, Texas. Measurements were taken at 218 marks (one per mile) and included static GPS, RTN GPS, geodetic leveling, astro-geodetic deflections of the vertical using the Swiss DIADEM camera, absolute gravity, gravity gradients and LIDAR. This region was chosen for many factors including the availability of GRAV-D airborne gravity over the area, its relatively low elevation (220 meter orthometric height max), its geoid slope (about 130 cm over 300 km), lack of significant topographic relief, lack of large forestation, availability of good roads, clarity of weather and lack of large water crossings.
This talk will outline the initial results of the survey, specifically the comparison of various geoid slopes over this region: gravimetric geoid models (with and without airborne gravity), minimally constrained GPS and leveling and from astro-geodetic deflections of the vertical.

Consistency of Crustal Loading Signals Derived from Models and GPS: Inferences for GPS Positioning Errors
After applying corrections for surface load displacements to a set of station position time series determined using the Global Positioning System (GPS), we are able to infer precise error floors for the determinations of weekly dN, dE, and dU components. The load corrections are a combination of NCEP atmosphere, ECCO non-tidal ocean, and LDAS surface water models, after detrending and averaging to the middle of each GPS week. These load corrections have been applied to the most current station time series from the International GNSS Service (IGS) for a global set of 706 stations, each having more than 100 weekly observations. The stacking of the weekly IGS frame solutions has taken utmost care to minimize aliasing of local load signals into the frame parameters to ensure the most reliable time series of individual station motions. For the first time, dN and dE horizontal components have been considered together with the height (dU) variations.
By examining the distributions of annual amplitudes versus WRMS scatters for all 706 stations and all three local components, we find an empirical error floor of about 0.65, 0.7, and 2.2 mm for weekly dN, dE, and dU. Only the very best performing GPS stations approach these floors. Most stations have larger scatters due to other non-load errors. These global error floors have been verified by studying differences for a subset of 119 station pairs located within 25 km of each other. Of these, 19 pairs share a common antenna, which permits an estimate of the fundamental electronic noise in the GPS estimates: 0.4, 0.4, and 1.3 mm for dN, dE, and dU. The remaining 100 close pairs that do not share an antenna include this noise component as well as errors due to multipath, equipment differences, data modeling, etc, but not due to loading or direct orbit effects since those are removed by the differencing. The WRMS dN, dE, and dU differences for these close pairs imply station error floors of 0.8, 0.9, and 2.1 mm, respectively, almost the same as the error floors inferred from the global results where orbit errors should be fully expressed. This match implies that GPS orbit errors are only a minor part of the IGS weekly position uncertainties. A similar comparison for periodic signals implies that about a third of the GPS draconitic harmonics probably arise from sources local to the stations whereas the remaining two-thirds comes from orbital effects.

Subdaily Alias and Draconitic Errors in the IGS Orbits
Harmonic signals with a fundamental period near the GPS draconitic year (351.2 d) and overtones up to the 8th multiple have been observed in the power spectra of nearly all products of the International GNSS Service (IGS), including station position time series [Ray et al., 2008; Collilieux et al., 2007; Santamaria-Gomez et al., 2011], apparent geocenter motions [Hugentobler et al., 2008], and orbit jumps between successive days and midnight discontinuities in Earth orientation parameter (EOP) rates [Ray and Griffiths, 2009]. Ray et al. [2008] suggested two mechanisms for the harmonics: mismodeling of orbit dynamics and aliasing of near-sidereal local station multipath effects. King and Watson [2010] have studied the propagation of local multipath errors into draconitic position variations, but orbit-related processes have been less well examined.
Here we elaborate our earlier analysis of GPS orbit jumps [Griffiths and Ray, 2009; Gendt et al., 2010] where we observed some draconitic features as well as prominent spectral bands near 29, 14, 9, and 7 d periods. Finer structures within the sub-seasonal bands fall close to the expected alias frequencies of subdaily EOP tide lines but do not coincide precisely. While once-per-rev empirical orbit parameters should strongly absorb any subdaily EOP tide errors due to near-resonance of their respective periods, the observed differences require explanation. This has been done by simulating known EOP tidal errors and checking their impact on a long series of daily GPS orbits. Indeed, simulated tidal aliases are found to be very similar to the observed orbital features in the sub-seasonal bands. Moreover and unexpectedly, some low draconitic harmonics were also stimulated, potentially a source for the widespread errors in most IGS products.

How do we achieve confidence with our Real Time (RT) work? What pitfalls should we avoid? Are there guidelines to follow to help us with our procedures? How accurate are the Real Time Networks? Should I be using Glonass?
Those are just some of the common questions surveyors, engineers and other geospatial professionals ask when they go to the field to obtain RT GNSS positional coordinates. Because so much of RT GNSS positioning is transparent to the user and is entirely dependent on the field technician to bring back good data, it is incumbent on that technician to follow correct procedures and certain criteria to ensure a successful campaign. This webinar will show the recommended specific criteria to achieve 4 different grades of precision at the 95% confidence level, and will present the critical areas that can affect our RT data collection.

Evaluation of GPS Orbit Prediction Strategies for the IGS Ultra-rapid Products
To serve real-time and near real-time users, the International GNSS Service (IGS) produces Ultra-rapid GPS & GLONASS orbit product updates every 6 hr. Each is composed of 24 hr of observed orbits, with an initial latency of 3 hr, together with propagated orbits for the next 24 hr. We have studied how the orbit prediction performance varies as a function of the arc length of the fitted observed orbits and the parameterization strategy used to estimate empirical solar radiation pressure (SRP) effects. To focus on the dynamical aspects of the problem, nearly ideal conditions have been adopted by using IGS Rapid orbits as observations and known Earth orientation parameters (EOPs). Performance was gauged by comparison with Rapid orbits as truth by examining WRMS and median orbit differences over the first 6 hr and the full 24 hr prediction intervals, as well as the stability of the Helmert alignment parameters. Note that the actual IGS Ultra-rapid accuracy is limited mostly by rotational instabilities, especially about the Z axis due to errors in near real-time and predicted UT1 values.
We found that observed arc lengths of 40 to 44 hr produce the most stable and accurate predictions during 2010. Two versions of the extended SRP orbit model by the Centre for Orbit Determination in Europe (CODE) were tested. Adjusting all 9 SRPs (offsets plus once-per-rev sines and cosines in each D,Y,B component) for each satellite shows smaller mean subdaily, scale, and origin translation differences. On the other hand, when the 4 once-per-rev SRPs in the D and Y directions are held fixed, then smaller, more stable rotational differences are obtained. A combined strategy of rotationally aligning the 9-SRP results to the 5-SRP frame should give optimal predictions with about 15 mm mean WRMS over the first 6 hr and 35 mm over 24 hr. Actual Ultra-rapid performance will be degraded due to larger errors in the available near real-time observed orbits and EOP predictions.

Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software.
To help meet the needs of the high-precision GNSS community, the National Geodetic Survey (NGS) now operates an absolute antenna calibration facility. Located in Corbin, Virginia, this facility uses field measurements and actual GNSS satellite signals to quantitatively determine the carrier phase advance/delay introduced by the antenna element. The NGS facility was built to serve traditional NGS constituents such as the surveying and geodesy communities, however calibration services are open and available to all GNSS users as the calibration schedule permits. All phase center patterns computed by this facility will be publicly available and disseminated in both the ANTEX and NGS formats.
We describe the NGS calibration facility, and discuss the observation models and strategy currently used to generate NGS absolute calibrations. We demonstrate that NGS absolute phase center variation (PCV) patterns are consistent with published values determined by other absolute antenna calibration facilities, and compare absolute calibrations to the traditional NGS relative calibrations.

Although originally designed to enable accurate positioning and time transfer, the Global Positioning System (GPS) has also proved useful for remote sensing applications. In this study, GPS signals are used to measure snow depth via GPS interferometric reflectometry (GPS-IR). In GPS-IR, a GPS antenna receives the desired direct signal as well as an indirect signal which reflects off of the ground or snow surface. These two signals interfere, and the composite signal recorded by the GPS receiver can be post-processed to yield the distance between the antenna and the reflecting surface, that is, distance to the snow surface.
We present the results of a new snow depth product for the state of Minnesota over the winter of 2010-2011. Although single-station examples of GPS snow depth measurements can be found in the literature, this is one of the first studies to compute GPS snow depth over a large regional-scale network. We chose Minnesota because the state Department of Transportation runs a network of continuously operating reference stations (CORS) with many desired characteristics: freely available data, good GPS station distribution with good proximity to COOP weather stations, GPS stations located adjacent to farm fields with few sky obstructions, and receiver models known to have sufficient data quality for GPS-IR.
GPS-IR with CORS has many advantages over traditional snow depth measurements. First, because we leverage existing CORS, no new equipment installations are required and data are freely available via the Internet. Second, GPS-IR with CORS measures a large area, approximately 100 m2 around the station and 20 m2 per satellite.
We present snow depth results for over 30 GPS stations distributed across the state. We compare the GPS-IR snow depth product to COOP observations and SNODAS modeled estimates. GPS-IR snow depth is one of the few independent data sources available for assessment of SNODAS. Ideally snow depth via GPS-IR will be available for ingestion into operational systems such as NOAA-NWS streamflow, weather and climate forecast systems at other locations across the US in the not too distant future.

As part of the National Geodetic Survey's 10 year plan for the modernization of the National Spatial Reference System (NSRS), entirely new horizontal and vertical datums will be developed to replace the existing NAD 83 and NAVD 88. The changes in these datums will have a significant impact on the users of geodetic data nation wide. This presentation will describe the existing components of NSRS and the rational for the need to adopt new reference frames.

As part of the National Geodetic Survey's 10 year plan for the modernization of the National Spatial Reference System (NSRS), entirely new horizontal and vertical datums will be developed to replace the existing NAD 83 and NAVD 88. The changes in these datums will have a significant impact on the users of geodetic data nation wide. This presentation will describe the existing components of NSRS and the rational for the need to adopt new reference frames.

Quantifying Load Model Errors by Comparison to a Global GPS Time Series Solution Various space geodetic studies over the past two decades have shown that temporal variations in the distribution of ocean, atmospheric, and continental water masses cause detectable vertical displacements of the Earth's surface. Unlike most past research that focused on a single load component for only vertical motions, we have included the horizontal, as well as vertical, components and considered atmosphere, non-tidal ocean, surface water load models. Our geodetic solution is the most current reprocessed station time series from the International GNSS Service (IGS) for a global set of 706 stations, each having more than 100 weekly observations. The long-term stacking of the weekly frame solutions has taken utmost care to minimize aliasing of local load signals into the frame parameters to ensure reliable time series of individual station motions. Our reference load model consists of components from NCEP atmosphere (corrected for high-resolution topographic variations), ECCO non-tidal ocean, and LDAS surface water (cubic detrended over 1998 to 2011 to remove inter-annual artifacts), then combined, linearly detrended, and averaged to the middle of each GPS week as a posteriori corrections. This reference model reduces the WRMS scatters of about 72, 63, and 87% of GPS station dN, dE, and dU components, respectively. Alternative load models, for individual components or the total, can be tested against the same set of GPS time series to determine their relative accuracy. For example, not removing a cubic trend from the LDAS surface water loads causes a global average quadratic increase in WRMS scatters of about 0.1, 0.1, and 0.5 mm in dN, dE, and dU. The method is sensitive to load model error differences at the level of about 0.1 mm in the horizontal components and about 0.2 to 0.3 mm in the vertical due to residual load aliasing in the GPS time series. We will report relative accuracy differences for a range of load model pairs.

ICON (Ionosphere over CONus) was an experimental ionosphere model developed at NGS between 2002 and 2005. It relies solely on ambiguous phase data, and uses a mathematical truth to arrive at absolute TEC values. This presentation discusses ICON, and another NGS-sponsored model, called MAGIC (which ultimately became the SWPC's USTEC engine). Unlike MAGIC, which was a 3-D (plus time) model, ICON was a 2-D (shell, plus time) model. ICON never left the experimental stages, due to a variety of instabilities and the generally better performance of MAGIC. However the mathematical solution to arrive at UNambiguous TEC from ambiguous phase data remains valid and may prove useful in the future.

This presentation shows the original work that led to VDatum and the pilot projects it supported.

Consistency of Crustal Loading Signals Derived from Models and GPS: A Re-examination
Various space geodetic studies over the past two decades have detected vertical displacements of the Earth's surface caused by temporal variations in the distribution of ocean, atmospheric, and continental water masses. Most past research has focused on a single component of the mass load and till now only vertical motions have been examined. Successively stronger correlations have been seen as improvements have been made in the load models as well as in measurements by the Gravity Recovery and Climate Experiment (GRACE) of surface mass changes and by the Global Positioning System (GPS) of station height variations. Initial comparisons of modeled surface mass load displacements with GPS heights were most successful for areas with large signals, such as the Amazon River basin, where the amplitude of annual height variations reaches ~13 mm. Following large-scale efforts to reprocess historic GPS data series with modern analysis methods, the most recent results find that mass load corrections reduce the WRMS scatter of GPS verticals for ~77% of global networks of more than 100 stations.
We have re-examined this problem but included the horizontal, as well as vertical, components and used the most current station time series from the International GNSS Service (IGS) for a global set of 706 stations, each having more than 100 weekly observations. The long-term stacking of the weekly frame solutions has taken utmost care to minimize aliasing of local load signals into the frame parameters to ensure the most reliable time series of individual station motions. Using a combination of NCEP atmosphere, ECCO non-tidal ocean, and LDAS surface water load models (averaged to the middle of each GPS week) as a posteriori corrections, the WRMS GPS scatters are reduced for 72, 63, and 87% of station dN, dE, and dU components, respectively. Fitted annual amplitudes are correspondingly reduced for similar fractions of stations. The weighted mean dU annual amplitude drops from 3.9 to 1.7 mm with load corrections applied. An absence of dU improvement is nearly only limited to island and coastal sites with small load effects, but degradations for dN and dE are more widespread. Some stations are clearly exceptional due to data problems. The quality and global coverage of current GPS time series has reached a point that they can be used as an independent reference to precisely evaluate the relative performance of competing load models.

To achieve the best airborne gravity data accuracy possible, the GPS position solutions must provide not just accurate and precise positions, but accurate and precise velocities and accelerations to be used in calculating gravity corrections. To our knowledge, no head-to-head comparisons have been done of available kinematic processing techniques with a focus on producing good airborne gravity results.
ORIGINAL GOALS:
1. 0.5 mGal or less two-sigma values (precision) for free-air disturbances calculated with different GPS position solutions, but the same gravity processing.
2. Close comparisons to EGM08 (accuracy), the best available global gravity model (Pavlis, et al., 2010), in an area where EGM08 is well-constrained.
Thus, in Fall 2010 the National Geodetic Survey announced the “Kinematic GPS Challenge� to the entire GPS community. The Challenge solicited position solutions for two GRAV-D airborne gravity flights done in Louisiana in Fall 2008. The flights are described in the data section. The response of the community was outstanding, with some groups submitting multiple solutions: Participating groups: 10; Solutions for each flight: 16; Total solutions (for 4 gravity lines): 64. GPS processing types span the range of differential and PPP solutions, with different methods developed by each group. The results are presented anonymously here (each solution presented with a unique f## designator rather than the software’s & developer’s names), protecting the GPS participants while they discuss these results but allowing the airborne gravity community to benefit from the early conclusions.

This presentation provides an overview of why geodesy and datums are important to GIS. Various tools and products are covered so the user is aware of how they can use and access the NSRS and its data.

National Geodetic Survey Director, Juliana Blackwell, gave a presentation on NGS’s Gravity for the Redefinition of the American Vertical Datum (GRAV-D) program at the Management Association for Private Photogrammetric Surveyors (MAPPS) winter conference held January 22-23, 2012. MAPPS is an association of photogrammetry, mapping, and geospatial firms, and this briefing discussed the importance of GRAV-D and how MAPPS members and NGS can work together and support one another towards common goals. The new vertical datum in development by NGS will be important to both the Geographic Information Systems (GIS) and MAPPS communities, which rely on accurate elevations to perform their missions.

New Revised CORS Coordinates in IGS08 epoch 2005.00 and NAD 83 (2011/MA11/PA11) epoch 2010.00

As part of the continuing efforts to improve the National Spatial Reference System (NSRS), NOAA's National Geodetic Survey (NGS) has performed the National Adjustment of 2011 (NA2011). This adjustment yielded updated North American Datum of 1983 (NAD 83) coordinates on passive control stations with positions determined using Global Navigation Satellite System (GNSS) technology. It is a simultaneous least-squares adjustment of nearly 80,000 passive control stations using a nationwide network of over 400,000 GNSS vectors that represent over 4100 survey projects spanning from the mid 1980s to August 2011. NA2011 is constrained to current NAD 83 coordinates of the NGS Continuously Operating Reference Station (CORS) network, which is a GNSS-based “active� control system and the geometric foundation of the NSRS. These NAD 83 CORS coordinates were determined in the NGS Multi-Year CORS Solution (MYCS) through a combined solution of all CORS GNSS data from 1994 to April 2011. Constraining NA2011 to the MYCS optimally aligns the GNSS passive control with the active control, providing a unified reference frame. The resulting realization gives positions at an epoch date of January 1, 2010, and it is formally designated as NAD 83(2011) epoch 2010.00. To ensure consistency in the NSRS, NGS developed a new hybrid geoid model (GEOID12) for concurrent release with NA2011. GEOID12 is based on a new gravimetric geoid model (USGG2012) modified using NAD 83(2011) ellipsoid heights on vertical bench marks. To improve access to the NSRS, NGS developed a new datasheet format that will provide some of the new information associated with NA2011, such as detailed accuracy information. The NGS “Bluebook� process for submitting control surveys for publication has also been improved, including a new version of the ADJUST least-squares adjustment program. This workshop describes the methods and results of NA2011, as well as the MYCS that provides the control for NA2011. The workshop also gives an overview of GEOID12, the new NGS Datasheet format, and other updates, such as the new version of ADJUST and new GIS-compatible products and services. NA2011 improves how NGS meets its wide range of customer needs in providing the basis for accurate and reliable georeferencing throughout the US and its territories. Completion of NA2011 – together with related products and services – represents a significant step toward a more integrated NGS, in terms of both better positions and improved access to the NSRS.

Juliana Blackwell, Director, NOAA’s National Geodetic Survey (NGS), presented an overview of why geodesy and datums are important to geographic information systems at the National States Geographic Information Council (NSGIC) meeting held February 29 to March 1 in Annapolis, MD. Included in the presentation was a background of NGS’ modernization efforts for the National Spatial Reference System (NSRS) that are currently underway, as well as key products and services of interest to the GIS (geographic information systems) community, including NGS’s Gravity for the Redefinition of the American Vertical Datum (GRAV-D) initiative, the National Adjustment of 2011 (NA2011) project, the new GEOID12 gravity model, and new GIS tools and datasets for display and analysis of survey data. An overview of the socio-economic benefits of NOAA/NGS products and services will also be provided.

Surveyors use Real Time GNSS (RT) technology becauseit’s a fast, efficient (labor saving) positioning tool that can yield survey grade coordinates used in a wide variety of applications. But, how good do you feel about the data you are producing with your real time gear? It is all “black box� technology after all. Are the data collector position quality values displaying precision or are they displaying accuracy and at what confidence level? What position deltas would you expect if you get another shot at a different time or with different weather? What are the factors that might be affecting your data, anyway? Would it be better to use a new real time network (RTN)to get your data? Is there any way to have real confidence with a RT established position? As we can see, there are a lot of questions with this technology and the answer to all of them is: “It depends�. That’s why NOAA’s National Geodetic Survey (NGS) has produced a set of single base RT user guidelines that recently left draft status to become an official NGS document. This workshop will discuss how you can have real confidence with real time work and go over the important criteria for the surveyor to achieve successful field campaigns based on the guidelines. Topics of discussion for best methods for the field include: constraining local monumentation, DOP, weather conditions, data collection parameters,multipath, how RT works, how RT doesn’t work, and many others emphasizing the attendees’ area of interest.

Recent and near-future changes in the geodetic datums and other developments being done by NGS are presented by the California Geodetic Advisor. She will: - Discuss how the new geodetic reference frame--IGS08-- was realized, - Detail the process for the nationwide adjustment of ~80,000 passive stations, - Explain the development of the upcoming GEOID12 gravity model - Introduce the RTN Validation initiative. Looking to the far future (10 years), you will learn about the developments that have been initiated to: - totally revamp the horizontal and vertical datums that define the NSRS, - obtain airborne gravity measurements to develop a geoid model accurate to 1 cm, - collect and analyze data for a Gravity Slope Validation Survey. There will be demonstrations of NGS software and online tools: - DSWorld for mapping NGS control locations in Google Earth, - DSWorld for submitting database corrections and updates (recovery notes), - VDATUM for relating tidal datums to geodetic datums - HTDP for getting different epoch coordinates

NGS Director, Juliana Blackwell, gave the keynote address at The Hawaii Pacific Geographic Information Systems (GIS) Conference 2012 held in Honolulu, HI March 5 to 9, 2012. Ms. Blackwell's presentation highlighted NGS' and NOAA's geospatial activities in the Pacific region. Topics covered included an overview of selected NOAA geospatial data and services supporting mapping and charting, comprehensive ocean and coastal planning, new approaches for visualizing and using NOAA data, including the latest mobile applications, and the development of a new NOAA Geospatial Platform for access to the breadth of NOAA's geospatial data, services, and applications.

Understanding the relationships between vertical datums is important, especially when converting elevations from one datum to another. Unfortunately, the various datums are not very far apart and it is easy to make mistakes adding or subtracting datum shifts. The presentation will show the basic relationships among common datums and advocate an easy to understand method of datum conversion.

The National Geodetic Survey has readjusted the passive mark network throughout the United States to reflect the most accurate positions of the CORS network. The adjustment results and their impacts on Minnesota will be discussed.

Technology has changed the face of surveying and mapping, and the National Geodetic Survey (NGS) is at the forefront in the implementation of many of these technologies to provide the Nation with a consistent and accurate reference system. NGS produces the National Spatial Reference System (NSRS) ensuring projects have the consistency and accuracy desired. There are many tools available to access the NSRS and these will be highlighted during this session. In particular, DS-World, CORS and the Online Positioning User Service (OPUS) will be discussed. Using Google Earth, DS-World, makes it possible for users to display the million-plus geodetic survey marks and the GPS Continuously Operating Reference Stations (CORS) that make up the NSRS. This useful tool can display all the survey marks available in a particular geographic area and the associated information about each point, including its description, position, and other information gathered when the mark was set. NGS’ OPUS program is highly automated and requires minimal user input accessing the network of CORS for determining ones position. With OPUS, users can obtain high-accuracy NSRS coordinates, using only a clear view of the sky and a survey-grade GPS receiver. OPUS processes GPS data files along with CORS coordinates to provide results consistent with those of other users. Many variations have and are evolving. There are many other developments occurring in NGS that will be presented. These include: NGS role with the development of real time GPS; Modernization of the NSRS; the new adjustment (to be completed by 2011); and the GRAV-D program and how it may change the way we obtain vertical heights.

Presentation is a 2-hour talk on the background and components of the NGS National Height Modernization Program, including how it fits into NGS' Ten-Year Plan.

Changing Geodetic Advisor Program LEARNING/CONT EDUCATION: NGS Resources Non-NGS CGPS Data/Info—PBO and CSRC OPUS: S, RS, DB, Projects HTDP Datasheet Format/Content Changes VDATUM DSWORLD Demonstration

NSRS Ref frame improvements: For CORS, for passive, Geoid model; NSRS Evolution: GRAV-D, GSVS, NSRS revolution; NGS FY12 Budget & Geodetic Advisor Program; Coastal Products & Services: Shoreline Change, VDATUM, SLR, GLOSS, CSC; Lightning topics

This presentation discusses the status of the national Continuously Operating Reference Station (CORS) network and the recent multi-year CORS solution (new published CORS coordinates), the status of the National Adjustment of 2011 (forthcoming new published coordinates on passive network stations), and the next generation (in about a decade) of national horizontal and vertical datums.

This presentation discusses the NGS Continuously Operating Reference Station (CORS) network, the recent multi-year CORS solution (new CORS coordinates), the NGS Online Positioning User Service (OPUS), the National Adjustment of 2011 (forthcoming new coordinates for passive control network), the NGS Ten-year Plan / plans for new datums (in about a decade), DSWorld software, forthcoming changes to NGS datasheets, the Geoid Slope Validation Survey of 2011, and other topics.

On September 6, 2011, the National Geodetic Survey (NGS) published new coordinates for the nationwide continuous GPS network called CORS, which had not been updated in 9.5 years. The official datum of the National Spatial Reference System is still NAD83 but the realization of the datum changes with each adjustment that generates new coordinates. This talk will explain what the metadata should include, particularly in California, and give a few examples of the differences among coordinates, between 1986 and present, even if all are referenced to “NAD83.� NGS anticipates that, in 10 years, the NAD83 datum will be replaced by a truly geocentric datum that will be related to the International Terrestrial Reference Frame datum. Although the horizontal position (latitudes and longitudes) will of course change, it is notable that the ellipsoid heights could differ by 0.5 meters.

Conclusions • IGS produces Ultra-rapid ERPs with subdaily resolution & high accuracy – observed ERPs updated every 6 hr with 15 hr latency – PM accuracy roughly similar to IGS Finals: 25 to 30 μas – IGS Rapid PM accuracy may be even better: 15 to 16 μas – IGU dLOD accuracy may be better than IGS Finals: ~5 μs – further study needed to assess accuracy of IGS ERPs • Main (systematic) error components are probably: – errors in IERS subdaily EOP tide model – orbit mis-modeling (draconitic signals) – instabilities in terrestrial reference frame (though none detected directly) • IGS Ultra-rapid PM predictions better than operational services – IGU dLOD predictions similar to operational service • IGS Ultra-rapid ERP observations & predictions should be assimilated by operational EOP prediction services !

The International GNSS Service (IGS) is preparing for a second reanalysis of the full history of data collected by the global network using the latest models and methodologies. This effort is designed to obtain improved, consistent satellite orbits, station and satellite clocks, Earth orientation parameters (EOPs) and terrestrial frame products using the current IGS framework, IGS08/igs08.atx. It follows a successful first reprocessing campaign, which provided the IGS input to ITRF2008. Likewise, this second campaign (repro2) should provide the IGS contribution to the next ITRF. We will discuss the analysis standards adopted for repro2, including treatment of and mitigation against non-tidal loading effects, and improvements expected with respect to the first reprocessing campaign. International Earth Rotation and Reference Systems Service (IERS) Conventions of 2010 are expected to be implemented. Though, no improvements in the diurnal and semidiurnal EOP tide models will be made, so associated errors will remain. Adoption of new orbital force models and consistent handling of satellite attitude changes are expected to improve IGS clock and orbit products. A priori Earth-reflected radiation pressure models should nearly eliminate the ~2.5 cm orbit radial bias previously observed using laser ranging methods. Also, a priori modeling of radiation forces exerted in signal transmission should improve the orbit products. And use of consistent satellite attitude models should help with satellite clock estimation during Earth and Moon eclipses. Improvements of the terrestrial frame products are expected from, for example, the inclusion of second order ionospheric corrections and also the a priori modeling of Earth-reflected radiation pressure. Because of remaining unmodeled orbital forces, systematic errors will however likely continue to affect the origin of the repro2 frames and prevent a contribution of GNSS to the origin of the next ITRF. On the other hand, the planned inclusion of satellite phase center offsets in the long-term stacking of the repro2 frames could help in defining the scale rate of the next ITRF.

The gravity field is directly related to the structure of the Earth and how its mass is distributed. Every piece of mass creates a potential of gravity (geopotential) that drops off with distance. The cumulative effect of all these produces the Earth's gravity field. This session will focus on the relationship between various aspects of the Earth's gravity field such as the geoid, geopotentials, gravity, deflections of the vertical, and physical heights (e.g., above mean sea level). It covers different means of observing the gravity field and how they are combined to produce models for height determination both at global scales, such as the World Height System, and locally for National Vertical Datums.

The National Geodetic Survey (NGS) is responsible for maintaining both the horizontal and vertical datums within the U.S. National Spatial Reference System (NSRS), which are the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88), respectively. NGS periodically produces hybrid geoid height models that transform between these datums to facilitate GPS/leveling in surveying as well as other engineering and scientific activities. The GEOID12 model represents the latest effort in this series. However, both NAD 83 and NAVD 88 have significant systematic problems, which the current hybrid geoid height models faithfully replicate. While the datums remain internally consistent (i.e., precise) they are inconsistent with other reference systems at the meter level (i.e., not accurate). Comparisons at tide gauges and with global satellite gravity field models demonstrated a meter level cross-continent trend in NAVD 88 likely due to accumulated leveling errors in the adjustment that created it. Likewise NAD 83 is known to have a 2.2 meter offset from IGS 2008. The Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project was started to realize a new vertical datum that is both accurate and precise. The aim of the project is to produce a gravimetric geoid height model that is accurate to cm-level and can be combined with an improved geometric reference frame to produce similarly improved physical heights, removing entirely the need to have “hybrid� geoid models which absorb systematic datum errors. Several factors are critical to ensuring this works. In anticipation of its adoption in 2022 at the completion of GRAV-D, an optimum geopotential surface (geoid) was recently selected based on comparisons with tidal bench marks around Canada and the United States and some portions of the Caribbean. A geopotential value of 62,636,856.00 m2/s2 best fit available data. This value is the same as that adopted by the International Astronomical Union (IAU) & the International Earth Rotation and Reference Systems Service (IERS) and is one of many that have been offered as the best representative of global mean sea level (MSL). Comparisons all around the North American continent with tide gauges, satellite altimeter measurements of the ocean surface, and models of ocean height variability all support adoption of this number as the best estimate of MSL for North America and future vertical reference systems defined for the United States and Canada. Canada will be adopting this value and a geoid height model based on it as their official vertical datum in 2013 while the United States will follow suit in 2022. The United States continues to collect aerogravity to remove systematic errors in the terrestrial gravity data holdings to ensure that a cm-level of accuracy is achieved. This is on track and should be accomplished as planned in 2022 with a new vertical datum realized by a gravimetric geoid height model and GNSS observations.

In the United States, since the mid-late 1990’s, the Height Modernization Program has worked with the user community through education, and providing models, tools, and guidelines to enable access to the country’s official vertical reference frame, the North American Vertical Datum of 1988 (NAVD 88), using the Global Navigation Satellite System (GNSS). The program has focused on using data from stations with accurate leveled orthometric heights and high accuracy GNSS ellipsoid heights together with a gravimetric geoid model to create a geoid model that is fit specifically to NAVD 88. The accuracy of the geoid model and the capability of GNSS to measure heights have greatly improved. Users expect faster, more accurate results. But even with Height Modernization, maintaining the NAVD 88 through passive control and leveling is resource intensive. In dynamic regions in particular, the surveying community using these new technologies can now see how the changes in positions over time impact their work. Movement and velocity models have to be built into the process, and the very definition of the national datum must be something we can maintain. Like many other countries, the National Geodetic Survey (NGS) has come to the conclusion that this is only possible using an accurate gravity model and GNSS. In ten years, NGS will be replacing the NAVD 88 with a GNSS based vertical reference frame. But now that that decision has been made, how do they implement a new reference frame on a country-wide or continent-wide scale that is so vastly different that the reference frame people have used for over a 140 years? While addressing the needs of the user community to access the NAVD 88 during the next decade, the Height Modernization Program must also prepare that same community for the transition to a new kind of reference frame. The Height Modernization Program plan will include components of education, models, tools, and guidelines that will bridge the old and new ways of accessing the vertical datum. NGS will work closely with other federal, state, and local mapping agencies and organizations to make sure the infrastructure and processes are in place to support access to a National Spatial Reference System that is global and dynamic.

The National Oceanic and Atmospheric Administration’s National Geodetic Survey (NGS) is planning substantial changes to the National Spatial Reference System (NSRS) – the national system of latitude, longitude, elevation, and related geodetic models and tools – which, when implemented in a decade or so, will positively impact surveying and mapping activities nationwide. The new NSRS will provide improved accuracy and efficiency in the nation’s positioning infrastructure through enhanced utilization of the Global Navigation Satellite System (GNSS) and other modern technologies. Planned changes to the NSRS include the definition of a new vertical datum to replace the North American Vertical Datum of 1988 (NAVD88) and the definition of a new geometric datum to replace the North American Datum of 1983 (NAD83). This presentation will review the current status of national datums and will present a description of the new datums, the need for their implementation, some of the outstanding issues yet to be resolved, and considerations for a smooth transition.

The National Geodetic Survey (NGS) has recently reprocessed the full history of Global Positioning System (GPS) data collected from 1994.0 to 2010.5 at stations of the International GNSS Service (IGS) global tracking network and at stations of the U.S. Continuously Operating Reference Stations (CORS) network managed by NGS. This reprocessing effort focuses on using the latest models and methodologies to accurately determine regularized positions and secular velocities for CORS relative to the International Terrestrial Reference Frame of 2008 (ITRF2008). The reanalysis consists of reducing the time series of RINEX observations to obtain a fully consistent set of GPS satellite orbits, Earth Orientation Parameters (EOPs) and weekly station positions using the NGS PAGES software. In order to achieve the best available tie to the global framework, reduction of RINEX observations is accomplished in two stages. The first stage is specifically designed to obtain orbits, EOPs and station positions for sites in the global network, consisting mostly of IGS stations. The products resulting from this first stage of the reanalysis were submitted to the recent IGS reprocessing campaign. The second stage is designed to obtain a time-series of weekly SINEX files containing in addition station positions for sites in the much denser CORS network. The CORS+global SINEX files are then stacked and aligned to ITRF2008 using the CATREF software from Institut Géographique National (IGN). The entire process results in positions and velocities for all CORS in a fully-consistent global framework that can be aligned to the ITRF accurately and consistently. Challenges in this work include: accounting for all position and velocity discontinuities, and tying a large and dense regional network to a global framework without causing significant distortions to the frame. Here, we present a summary of the automated strategies used for finding undocumented discontinuities, an assessment of distortions caused by tying the CORS network to the global frame and a discussion of the updated CORS velocity field.

Demands for accuracy are increasing and the use of geospatial technologies, such as Geographical Information Systems (GIS) continue to rise. But how often do you have problems with data not aligning in your GIS? Knowing how your data is collected in terms of reference systems, coordinate systems, and datums, is growing more important to ensure your data layers do align properly. The National Oceanic Atmospheric Administration’s National Geodetic Survey (NGS) provides the basis for the critical geospatial infrastructure called the National Spatial Reference System (NSRS). The NSRS consists of the North American Datum of 1983 (NAD83) and the North American Datum of 1988 (NAVD88). Come hear about the differences in datums and why this is important in your work and the USGS products. There are several programs (DS-World, OPUS) that will be discussed along with planned replacements to both NAD83 and NAVD88.

Regional Operational Site visits are held with CDOTs six regions annually to provide an update of the latest developments occurring in NGS and discuss specific projects the regions are working on. This year, in addition, training was provided on using OPUS-DB. Meetings were held on the following dates and locations: R1 - May 18, 2012 - Denver, CO R2 - May 3, 2012 - Pueblo, CO R3 - January 31, 2012 - Grand Junction, CO R4 - May 31, 2012 - Greeley, CO R5 - Scheduled for September 2012 R6 - May 1, 2012 - Denver, CO

NOAA’s National Geodetic Survey (NGS) conducts antenna calibrations of receiving antennas in order to provide more accurate access to the National Spatial Reference System (NSRS), as an essential service for the surveying, mapping, and engineering infrastructure of the U.S. Antenna calibrations are an essential component of GNSS data processing and are used by both vendor- and university-supplied software as well as NGS’ Online Positioning User Service (OPUS). It should be noted that NGS constituents use a much larger variety of antennas than are present in the IGS network. Therefore NGS is interested in providing calibrations for a wide variety of geodetic-grade antennas, from types in use at IGS reference stations to rover antennas not normally seen in the IGS network. Since 1994, NGS has computed relative antenna calibrations for more than 350 antennas. In recent years, the geodetic community has moved to absolute calibrations - the IGS adopted absolute antenna phase center calibrations in 2006, and NGS's CORS group began using absolute antenna calibration upon the release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD 83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and have been converted to absolute, it is considered best practice to independently measure phase center characteristics in an absolute sense. Consequently, NGS has developed and operates an absolute calibration system. These absolute antenna calibrations accommodate the demand for greater accuracy and for 2-dimensional (elevation and azimuth) parameterization. NGS will continue to provide calibration values via the NGS web site www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as well as the legacy ANTINFO format. The NGS absolute system is located in Corbin, Virginia, and uses field measurements and actual GNSS satellite signals to quantitatively determine the carrier phase advance/delay introduced by the antenna element. In this poster, we intend to cover several topics of interest to the IGS community, by: * describing the NGS calibration facility and assumptions which underpin the setup and method * discussing the observation models and strategy currently used to generate NGS absolute calibrations * demonstrating that NGS absolute PCO and PCV values are consistent with other IGS-sanctioned absolute antenna calibration facilities * outlining future planned refinements to the system * discussing features of the NGS Calibration Policy and Procedures documents, which outline the relationship between NGS and its customers

The recently released GEOID12 model provides an update for surveying and engineering applications requiring transformations between the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88). GEOID12 incorporates a number of recently completed adjustments to the NGS Database. The National Adjustment of 2011 (NA2011) was completed and released at the same time as GEOID12 and represents the most recent realization of ellipsoidal or geometric coordinates for bench marks. This complements recent adjustments to the leveled heights in several states particularly those in the central Gulf Coast region where subsidence is an issue. Underpinning this is the United States Gravimetric Geoid for 2012 (USGG2012) that incorporates gravity field observations from multiple satellite gravity missions (GRACE, GOCE). USGG2012 provides the fine detail that fills in the information in between the control data represented by both the GPS on leveled Bench Marks for 2012 (GPSBM2012) and archived values in the OPUS-DB on leveled Bench Marks for 2012 (OPUSDDBM12). The preponderance of these control points derive from GPSBM2012 (around 23,000) but the OPUSDBBM12 provides additional coverage to reduce interpolation across gaps in the GPSBM2012 coverage. The control data were used to develop a conversion surface with Least Squares Collocation following the same techniques used for GEOID03 and GEOID09. This surface provides the transformation necessary to change USGG2012 into GEOID12. It also provides insight into the expected shift between NAVD 88 and the future vertical datum of the United States to be implemented in 2022.

* Systematic rotations are a leading IGS error - they affect all core products except probably clocks * Sources include defects in: - IERS model for 12h + 24h tidal ERP variations - intra-AC product self-consistency & use of over-constraints - AC realizations of ITRF - models for GNSS orbit dynamics (SRP, gravity field variations) * Examine evidence in IGS products * Finals appear rotationally less stable than Rapids !

The International GNSS Service (IGS) continues to provide satellite orbits and clocks, station clocks, Earth orientation parameters (EOPs), and terrestrial reference frame products. Currently, there are three product lines, namely the IGS Final, the IGS Rapid, and the IGS Ultra-rapid. These products are made available on a weekly basis, with a delay up to 13 (for the last day of the week) to 20 (for the first day of the week) days. These products are the basis for the IGS terrestrial reference frame and are intended for those applications demanding the highest internal consistency and best quality. The IGS Rapid products have a quality comparable to that of the Final products. They are made available on a daily basis with a delay of about 17 hours after the end of the previous observation day. IGS Ultra-rapid products are released four times per day with 3 hours latency—i.e., released at 03:00, 09:00, 15:00, and 21:00 UTC—making them available for real-time and near real-time use. Contrary to all other IGS orbit products, the IGS Ultra-rapid orbit files contain 48 hours of tabular orbital ephemerides, and the start/stop epochs continuously shift by 6 hours with each update. The first 24 hours of each IGS Ultra-rapid orbit are based on the most recent GPS observational data. The next 24 hours of each file are predicted orbits, extrapolated from the observed orbits. Normally, the predicted orbits between 3 and 9 hours into the second half of each Ultra-rapid orbit file are most relevant for true real time applications. All other orbit products contain only the 24 hours from 00:00 to 23:45 UTC. The IGS generally aims to provide ~1 cm orbits and ~1 mm terrestrial frame products to meet the most demanding user needs. While the goal has not yet been met, the IGS has made good progress. Ray and Griffiths recently reported that the IGS GPS Final orbits have an accuracy better than 2.5 cm; the Rapids are of similar quality, with an inaccuracy of ~2.5 cm; and the 24h observed parts of the IGS Ultra-rapids have an accuracy of ~3.0 cm while the 24h predicted parts have an accuracy of about 5 cm. Inaccuracies of the IGS GLONASS orbits are about twice as large as for GPS. About half of the total error in the GPS orbits can be attributed to systematic time-varying rotational misalignment of the orbital frames (Griffiths and Ray, 2009; Gendt et al., 2010; Griffiths et al., 2012). Orbit mismodeling also contributes to these errors. Sub-daily alias and draconitic errors in the GPS orbits are largely caused by errors in the IERS diurnal and semi-diurnal EOP model (Griffiths et al., 2011). For most applications, the user of IGS orbit products will not notice significant differences between results obtained using the IGS Final and the IGS Rapid products. IGS weekly realizations of the combined terrestrial frame have accuracies of ~2 mm in each orthogonal horizontal component and ~5 mm in the vertical. The errors in the terrestrial frame probably arise mainly from inadequacies of the GNSS tracking stations, including the presence of uncalibrated radomes, near-field multipath effects and equipment changes, and mismodeling of tropospheric and ionospheric propagation delays. Many of these outstanding issues are indeed the focus of the IGS second reprocessing (i.e., IG2) campaign, the processing for which could be underway by early 2013. If all model changes intended for IG2 are in fact made, then the orbit and terrestrial frame errors should be reduced. However, there is currently no plan for a new IERS sub-daily EOP model or for mitigating inadequacies of the tracking stations, so one should temper their expectations for these aspects.

* Test effect of GRACE RL05 annual model fits from CSR - consider terms (2,0), (2,1), (2,2), & (3,1) * Compare GPS results for two extreme weeks - 1668 = 25 - 31 Dec 2011 - 1694 = 24 -30 Jun 2012 * Impacts at levels up to several mm * Other ACs should test & consider using in Repro2

Requested presentation to primary group within USGS who interfaces with public. The presentation covered the basics of NGS, the NSRS, datums, NGS tools and products such as DC-World, CORS, OPUS as well as NGS-USGS collaborative projects.

This presentation describes the NOAA/National Geodetic Survey’s network of permanent GNSS Continuously Operating Reference Stations (CORS) and the related Online Positioning User Service (OPUS) utility. The CORS network and OPUS both support centimeter-level positioning capability, thereby enhancing a broad range of user applications, including those demanding extremely high positional accuracy. The material presented should be of interest to professionals involved in surveying, mapping, GIS, and other geospatial disciplines. The CORS network comprises a network of approximately 2,000 sites, each containing a geodetic-quality GNSS receiver whose data are freely available via the Internet. Presentation topics include the development of the CORS network, CORS applications, and CORS data access. OPUS is an automated utility that processes submitted GNSS observation data with respect to the CORS network and provides positional results to the submitter via email, usually within minutes. The development, use, and applications of OPUS will be discussed.

Summary of NGS absolute gravity and related activities over time, emphasizing station coverage, GRAV-D, GSVS-11 and SAVSARP.

Demands for accuracy are increasing and the use of geospatial technologies, such as Geographical Information Systems (GIS) continue to rise. But how often do you have problems with data not aligning in your GIS? Knowing how your data is collected in terms of reference systems, coordinate systems, and datums, is growing more important to ensure your data layers do align properly.

The National Oceanic Atmospheric Administration’s National Geodetic Survey (NGS) provides the basis for the critical geospatial infrastructure called the National Spatial Reference System (NSRS) to ensure projects have the consistency and accuracy desired. The NSRS consists of the North American Datum of 1983 (NAD83) and the North American Datum of 1988 (NAVD88).

Come hear about the differences in datums and why this is important in your work. There are several programs (DS-World, OPUS) that will be discussed along with planned replacements to both NAD 83 and NAVD 88.

Demands for accuracy are increasing and the use of geospatial technologies, such as GIS continue to rise. But how often do you have problems with data not aligning in your GIS? Knowing how your data is collected in terms of reference systems, coordinate systems, and datums, is growing more important to ensure your data layers do align properly.

The National Geodetic Survey produces the National Spatial Reference System (NSRS) ensuring projects have the consistency and accuracy desired. The NSRS consists of the North American Datum of 1983 (NAD83) and the North American Datum of 1988 (NAVD88). There are many tools available to access the NSRS (DS-World, CORS, OPUS) and these will be highlighted during this session.

DS-World, makes it possible for users to display the million-plus geodetic survey marks and the GPS Continuously Operating Reference Stations (CORS) that make up the NSRS in GoogleEarth. This tool displays survey marks and its associated information. You can access, locate and survey these marks and tie your data layers directly to the NSRS and the most recent datums. NGS’ OPUS program is highly automated and requires minimal user input accessing the network of CORS for determining ones position. OPUS processes GPS data files along with CORS coordinates to provide results consistent with those of other users in the NSRS. There are many developments occurring in NGS that will be presented including the new adjustment, new datums (in 2022) and the GRAV-D program (which will change the way we obtain vertical heights).

Transitioning to the new reference frame NAD 83(2011)2010.00 from NAD 83(CORS96)2002.00 in the Pacific Northwest. Topics include: -National Spatial Reference System New NAD 83 reference frame: NAD 83(2011, MA11, PA11)epoch 2010.00 -Global Reference Frame Coordinates: IGS08(2005) -Review the change to absolute antenna calibrations -NA2011 completed (~80k passive marks) -GEOID12A (now available) -Review how CORS positions are computed with the MYCS -The OPUS Suite -OPUS Projects (beta) -Updating coordinates for the ORGN (Real-Time Network) from NAD 83(COR96)epoch 2002.00 to NAD 83(2011)epoch 2010.00

The National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) is responsible for defining, maintaining, and providing access to the National Spatial Reference System (NSRS) for states and territories of the United States. To best ensure the integrity of the NSRS, additional information outside of the U.S. is required. To that end, NGS has been engaged with Mexico for the past half-decade and Canada for the past two decades. The two ongoing satellite gravity missions, GRACE and GOCE, provide a broader reference system in which to define a unified vertical reference system for height determination. The IAG Sub-Commission 2.4c for Gravity and Geoid in North and Central America is specifically focused upon defining a geoid height model for that purpose. Together the United States, Canada, and Mexico have been working toward determining and fixing any systematic defects in national gravity datasets and making these mutually available. Most of the data in Canada have been deemed sufficient already by way of comparisons to global satellite gravity field models. Significant problems remain in American and Mexican data sets that need to be resolved. The Gravity for the Redefinition for the American vertical Datum (GRAV-D) project is the primary means for addressing this in the U.S., while Mexico has adopted a program that will revisit all base station ties to determine any systematic effects on derived relative gravity values. For the U.S., grids of aerogravity data have been integrated with the satellite models to provide a reference field for determining and fixing the systematic errors in over 1400 different surveys containing biases of to 6 mGal across regions of several hundreds of kilometers. The impact of removing these systematic effects was to remove many decimeters of error from the derived geoid height model and thereby move closer to the goal of a cm-level accurate model. Overflights into Canada and Mexico will likewise ensure integrity of the model across the U.S. border into the broader transnational region. Mexico has been engaged with countries in Central America and the Caribbean to conduct training on gravity collection and development of geoid height models, with several countries moving forward now with collection programs and data sharing. Data sharing with IAG Sub-commission 2.4.b, Gravity and Geoid in South America, has also been discussed with the intent to obtain data to the Equator and provide as much data as the IAG SC 2.4b group needs to complete their model. This will provide a seamless transition over the Americas consistent with the intent of a unified world height system.

The release of USGG2012 marks another step closer to a common North American Geoid and future Vertical Height System. The geopotential surface adopted in USGG2012 was determined after careful analysis of geopotential values at tide gauges around Canada and the United States spanning the Pacific, Gulf of Mexico, and Atlantic regions as well as parts of the Arctic. The intent was to determine a value that best fits tide MSL around the continent. Models of ocean topography were also used to mitigate local variations. Additionally, comparisons were made to multiple regional and global models to settle upon the optimal value, which will also be utilized in CGG2013. CGG2013 will mark the first use of a geoid height model to define a vertical datum in Canada. The United States is committed to moving to a similar model in 2022 after significant problems are resolved in the terrestrial data holdings used to make the models. The impact on Canadian regions is minimal but much more profound for regions in the U.S.A because of the aerogravity coverage. Aerogravity flights continue over the Great Lakes region to resolve some of these issues in the border region to ensure that these are more likely available for the generation of CGG2013 and the impending IGLD15 update. Aerogravity profiles have already been released for the Gulf Coast region and preliminary analysis does show that the cm-geoid is achievable for coastal regions.

The United States National Geodetic Survey (NGS) has embarked on a ten year project called GRAV-D (Gravity for the Redefinition of the American Vertical Datum). The purpose of this project is to replace the current official vertical datum, NAVD 88 (the North American Vertical Datum of 1988) with a geopotential reference system based on a new survey of the gravity field and a gravimetric geoid. As part of GRAV-D, the National Geodetic Survey plans to execute a set of "geoid validation surveys" at various locations of the country. These will be surveys designed to independently measure the geoid to provide a check against both the data and theory used to create the final gravimetric geoid which will be used in the geopotential reference system. The first of these surveys, known as the Geoid Slope Validation Survey of 2011 (GSVS11) was executed between July and October, 2011 in the west central region of Texas. The survey took place over a 325 kilometer line running more or less north-south from Austin to Corpus Christi, Texas. Measurements were taken at 220 marks (one per mile) and included static GPS, RTN GPS, geodetic leveling, astro-geodetic deflections of the vertical using the Swiss DIADEM camera, absolute gravity, gravity gradients and LIDAR. This region was chosen for many factors including the availability of GRAV-D airborne gravity over the area, its relatively low elevation (220 meter orthometric height max), its geoid slope (about 130 cm over 300 km), lack of significant topographic relief, lack of large forestation, availability of good roads, clarity of weather and lack of large water crossings. This talk will outline the results of the survey, specifically the comparison of various geoid slopes over this region: gravimetric geoid models (with and without airborne gravity), minimally constrained GPS and leveling and from astro-geodetic deflections of the vertical. In addition to a variety of interesting conclusions that came from the multi-technique survey, GSVS11 conclusively proved that the addition of recent GRAV-D airborne gravity data reduced the errors in gravimetric geoid models in this region to 1 cm over all wavelengths from 0 to 325 km.

The national Geodetic Survey (NGS) operates the On-line Positioning User Service (OPUS) as a means to provide GPS users easier access to the National Spatial Reference System (NSRS). OPUS allows users to submit their GPS data files to NGS, where the data will be processed against the Continuously Operating Reference Station (CORS) network to determine a position using NGS computers and software. This seminar will discuss: The history and development of OPUS products A discussion of OPUS accuracies (and things that affect the accuracies) Recommended collection procedures, data requirements, and data management A discussion of how to use each of the OPUS products and how they work An in-depth look at the output of OPUS and a discussion of OPUS statistics and quality indicators What can be done to make a poor solution better? A discussion on datums and coordinate systems for OPUS The recent CORS Multi-Year Solution and National Adjustment of 2011

In July of 2012, the National Geodetic Survey released the latest realization of NAD 83 and a new companion geoid model. This presentation will discuss a brief history of NAD 83, and reasons for its ongoing evolution. We will discuss the data used to produce the National Adjustment of 2011 (NA2011), and the concept (and need) to introduce velocities. Also discussed will be the relationships of geoid models to various versions of NAD 83 and what can happen if these relationships are ignored.

This is a formal presentation given for an hour at the start of a three-hour tutorial on Kinematic GPS and airborne gravimetry to 3rd-year surveying engineering students. The presentation focuses mostly on why and how NGS is updating the vertical datum in 2022 to a gravimetric geoid, as well as the field methodology used by GRAV-D to conduct large-scale airborne gravity campaigns year-round.

This is an overview of NGS' current projects and plans included in the draft 10-year plan, which will be effective in 2013. The presentation touches lightly on all the major programs and responsibilities of NGS, with projections about their futures.

There are many changes occurring at NGS, including new ways to access the National Spatial Reference System (NSRS). Pam Fromhertz, the CO State Geodetic Advisor, will cover the basics of the latest development occurring in NGS including the latest NAD 83 Adjustment (2011), the latest geoid model (12A), the new datasheets, as well as the tools to access the NSRS, such as DS-World and OPUS, particularly OPUS-DB. She will provide the status on heights in CO, CBLs and CORS. These topics will be discussed in much more detail at her 4 hour session at the PLSC Annual Survey Summit.

The California geodetic advisor will give updates on some of NGS' more popular programs, including the CORS network, OPUS, and DSWorld software. The adoption of ITRF2008 for CORS coordinates, the shift to absolute antenna calibrations, and the publication of NAD83(2011) geometric coordinates and GEOID12A are explained. There will be a review of the Datasheet fields, including the absence of accuracy orders, as well as clarification of textual metadata. In light of increasing concerns about planning for Sea Level Rise, there will be a brief primer on tidal datums and usage of VDATUM software, which incorporates geodetic datums.

Topics addressed include the doubling of NGS CORS in California in 2012, the development of Geoid12A, summary of recent datum tags for CORS and passive monuments, datasheet format changes,modification of the advisor program, and NGS' opportunities for continuing education which include posted presentations, recorded webinars, conference workshops and classroom training opportunities. Short demonstrations of Vdatum and DSWorld software conclude the presentation.

This talk presents basic information about the physical parameters of tides, king tides in California for Winter 2012/13, and explains tidal datums. Tidal data and application tools such as Inundation Duration are shown from CO-OPS webpages. Learning resources available on NGS "Science and Education" webpage are shown.

Technology, such as GPS and GIS make data collection and display easier. But knowing how your data is collected in terms of reference systems, coordinate systems, and datums, is growing more important to ensure compatibility between data sets.
The National Geodetic Survey produces the National Spatial Reference System (NSRS) ensuring projects have the consistency and accuracy desired. The NSRS consists of the North American Datum of 1983 (NAD83) and the North American Datum of 1988 (NAVD88). We will discuss the latest readjustment of NAD83 (2011), as well as a brief history of the datums. We will also discuss challenges in Colorado with Heights. The session will demonstrate the various tools (DS-World, CORS, OPUS) available to access the NSRS.
DS-World, makes it possible for users to display the million-plus geodetic survey marks and the GPS Continuously Operating Reference Stations (CORS) that make up the NSRS in GoogleEarth. This tool displays survey marks and its associated information. You can access, locate and survey these marks and tie your data layers directly to the NSRS and the most recent datums. If you are not using this, you will want to see this.
NGS’ OPUS program is highly automated and requires minimal user input accessing the network of CORS for determining ones position. OPUS processes GPS data files along with CORS coordinates to provide results consistent with those of other users in the NSRS. The latest version of OPUS (DB) will be presented so you will know how easy it is to create a new, user friendly datasheet displaying the positional information.
There are many developments occurring in NGS that will be presented including the new adjustment, new datums (in 2022) and the GRAV-D program (which will change the way we obtain vertical heights). These developments and how to use the tools will be demonstrated.
The presentation material has been divided into 5 sections.

The National Spatial Reference System includes latitude, longitude, height, gravity, scale, orientation, and time variations in those fields. The NSRS is used to provide geospatial referencing in topo, floodplain, and nautical maps. Shown are illustrations of the vectors between geodetic control stations utilized in NAD83 (2011), and the shift between that current and the superceded NAD83 (2007) realizations. The plan to improve the geoid model with airborne gravity measurements and revamp the national datums in about 10 years is discussed.

Advances in satellite geodesy have improved survey accuracies and provided new insights into our dynamic world, while revealing problems with the official reference frame used to measure them. The North American Datum of 1983 (NAD83) should be replaced by a more truly geocentric reference frame that accounts for tectonic plate motion. The National Geodetic Survey (NGS) will discuss the history of and modifications to NAD83, residual plate velocities, misalignment to the International Terrestrial Reference Frame (ITRF), how a new reference frame can address these issues and provide new benefits, and offer suggestions to users that will be affected.

A brief presentation of the proposed new U.S. vertical datum due out in 2023. Status report.

The mission of the National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) is “to define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation's economic, social, and environmental needs." NSRS is the nation’s system of latitude, longitude, elevation, and related data, models and tools, which provides a common, consistent, and accurate spatial reference system for a broad spectrum of users and applications. Over the years, technological developments and user accuracy requirements and demand have necessitated NGS to undertake several efforts to maintain and modernize the NSRS. These changes are all designed to improve the accuracy and accessibility of the NSRS, to the benefit of all geospatial professions and activities. Preparations are well underway for a major NSRS modernization makeover, to be realized in about a decade through a new generation of horizontal and vertical datums.

This presentation will describe the current status of the NSRS and will include information about accessing geodetic control descriptive and coordinate data, the national network of GNSS Continuously Operating Reference Stations (CORS), and the Online Positioning User Service (OPUS) utility. The recently published NAD83(2011) epoch 2010.00 datum realization for CORS, OPUS, and the passive control network and the corresponding geoid model (GEOID12A) will be described. The National Geodetic Survey Ten-Year Plan – a document that lays out a “mission, vision, and strategy” for NGS and the evolution of the NSRS over the next decade, including plans for the national geometric and geopotential datums of the future – will also be discussed.

All persons interested in the products and services provided by NGS are encouraged to attend, to ask questions, and to provide NGS with feedback regarding your geodetic requirements.

The mission of the National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) is “to define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation's economic, social, and environmental needs." NSRS is the nation’s system of latitude, longitude, elevation, and related data, models and tools, which provides a common, consistent, and accurate spatial reference system for a broad spectrum of users and applications. Over the years, technological developments and user accuracy requirements and demand have necessitated NGS to undertake several efforts to maintain and modernize the NSRS. These changes are all designed to improve the accuracy and accessibility of the NSRS, to the benefit of all geospatial professions and activities. Preparations are well underway for a major NSRS modernization makeover, to be realized in about a decade through a new generation of horizontal and vertical datums.

This presentation will describe the current status of the NSRS and will include information about accessing geodetic control descriptive and coordinate data, the national network of GNSS Continuously Operating Reference Stations (CORS), and the Online Positioning User Service (OPUS) utility. The recently published NAD83(2011) epoch 2010.00 datum realization for CORS, OPUS, and the passive control network and the corresponding geoid model (GEOID12A) will be described. The National Geodetic Survey Ten-Year Plan – a document that lays out a “mission, vision, and strategy” for NGS and the evolution of the NSRS over the next decade, including plans for the national geometric and geopotential datums of the future – will also be discussed.

The mission of the National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) is “to define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation's economic, social, and environmental needs." NSRS is the nation’s system of latitude, longitude, elevation, and related data, models and tools, which provides a common, consistent, and accurate spatial reference system for a broad spectrum of users and applications. Technological GNSS developments as well as user requirements and demand have resulted in extensive efforts to maintain and modernize the NSRS. These changes are all designed to improve the accuracy and accessibility of the NSRS, to the benefit of all geospatial professions and activities.
This presentation will describe the current status of the NSRS and will include information about the NGS network of GNSS Continuously Operating Reference Stations (CORS), the Online Positioning User Service (OPUS) utilities, and the online retrieval and updating options for geodetic control data. The current NAD83(2011) epoch 2010.00 datum realization and the corresponding geoid model (GEOID12A) will be described. Preparations are well underway for a major NSRS modernization makeover, to be realized in about a decade through a new generation of horizontal and vertical datums. Demonstrations of several interactive newer versions of NGS software will be given, including DSWorld, Vdatum (now does SPC conversions), NADCON, HTDP, and Translev for submitting Reset BM data.

http://meetingorganizer.copernicus.org/EGU2013/EGU2013-12412.pdf

The Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project, an official policy of the U.S. National Geodetic Survey as of 2007, is working to survey the entire U.S. and its holdings with high-altitude airborne gravimetry. The goal of the project is to provide a consistent, high-quality gravity dataset that will become the cornerstone of a new gravimetric geoid and national vertical datum in 2022. Over the last five years, the GRAV-D project has surveyed more than 25% of the country, accomplishing almost 500 flights on six different aircraft platforms and producing more than 3.7 Million square km of data thus far. This wealth of experience has led to advances in the collection, processing, and evaluation of high-altitude (20,000 – 35,000 ft) airborne gravity data. This presentation will highlight the most important practical and theoretical advances of the GRAV-D project, giving an introduction to each. Examples of innovation include: 1. Use of navigation grade inertial measurement unit data and precise lever arm measurements for positioning; 2. New quality control tests and software for near real-time analysis of data in the field; 3. Increased accuracy of gravity post-processing by reexamining assumptions and simplifications that were inconsistent with a goal of 1 mGal precision; and 4. Better final data evaluation through crossovers, additional statistics, and inclusion of airborne data into harmonic models that use EGM08 as a base model. The increases in data quality that resulted from implementation of the above advances (and others) will be shown with a case study of the GRAV-D 2008 southern Alaska survey near Anchorage, over Cook Inlet. The case study’s statistics and comparisons to global models illustrate the impact that these advances have had on the final airborne gravity data quality. Finally, the presentation will summarize the best practices identified by the project from its last five years of experience.

The On-line Positioning User Service (OPUS) is a National Geodetic Survey tool that provides you with a National Spatial Reference System (NSPS) coordinate via email in seconds using your own GPS data file. Several notable enhancements have either been implemented or are on the horizon. Underlying these enhancements are new CORS coordinates derived from a recently completed global GNSS network solution. This solution provides improved coordinates for all included CORS that are consistent with recognized reference systems such as the IGS08. OPUS-Net, currently under development, provides the same capabilities as OPUS Static, but with a more robust connection to the NSPS. OPUS-Projects, becoming operational in the summer of 2013, provides tools to handle GPS projects involving several sites occupied over several days. OPUS-Projects includes project visualization and management tools, enhanced processing options, and bluebooking support for an entire project. These and other new developments will be described.

The ionosphere is an unavoidable pathway through which all space-based radio communication, navigation, and surveillance signals must travel. Understanding ionospheric effects on radio signals propagation and using radio waves to study ionosphere phenomena have been active research areas for many decades. In recent years, global navigation satellite systems (GNSS) signals have gained recognition as a powerful and versatile means for ionospheric remote sensing because of their well-defined signal structure, global coverage, and distributed and passive nature. For satellite position, navigation, and timing engineers, the ionosphere is a complex and dynamic medium characterized by erratic behavior and spatial irregularities, which interfere with GNSS signal propagation, adversely impact applications such as aviation, intelligent transportation, guided weapons systems, precision agriculture, surveying, tracking and communications that have grown to rely on GNSS services. In this presentation, I will first discuss a globally-distributed autonomous data collection network of GNSS receiver arrays at strategically selected locations to facilitate a data-driven approach to study the complexity of ionospheric phenomena and their impact on GNSS. I will highlight several advanced GNSS receiver signal processing algorithms developed to process these data for scientific studies of ionosphere, for accurate estimation of ionosphere induced GNSS errors, and for robust and assured navigation during ionosphere disturbances. Ionosphere TEC distributions, higher order ionospheric error, space weather event characteristics, such as their temporal, spatial, spectral, and seasonal distributions, as well space plasma dynamics derived from the data will also be presented.

In July of 2012, the National Geodetic Survey released the latest realization of NAD 83 and a new companion geoid model. This presentation will discuss a brief history of NAD 83, and reasons for its ongoing evolution. We will discuss the data used to produce the National Adjustment of 2011 (NA2011), and the concept (and need) to introduce velocities. Also discussed will be the relationships of geoid models to various versions of NAD 83 and what can happen if these relationships are ignored.

Aerogravity collected in the Great Lakes region as a part of the Gravity for the Redefinition of the American Vertical Datum (GARV-D) provide an excellent opportunity to analyze the consistency of geoid height models of the region. This becomes imperative when considering that Canada is moving to adopt their Canadian Gravimetric Geoid 2013 (CGG2013) product as the basis for defining their vertical datum later this year. The aerogravity were not incorporated into the earlier United States Gravimetric Geoid 2012 (USGG2012) model, so they offer real insight into all models. An experimental geoid developed was developed using the aerogravity data. This model is consistent with the long wavelength signal from GRACE and GOCE incorporated into CGG2013 to ensure a more consistent direct comparison over the region. Additional comparisons are also made between the experimental model and USGG2012 and between CGG2013 and USGG2012. These comparisons take on added significance in view of the development of the International Great Lakes Datum of 2020 (IGLD 20) and the intended release of a gravimetric geoid height model for a vertical datum in the U.S. in 2022.

The International GNSS Service (IGS; igs.org) is a Scientific Service of the International Association of Geodesy (IAG; iag-aig.org), and provides Global Navigation Satellite System (GNSS) observational data and derived products to support a variety of positioning, navigation and timing applications. A sampling of these applications includes: precise orbit determination for low Earth orbit (LEO) satellites; precise time and frequency transfer; terrestrial reference frame realizations; and studies of crustal deformation, geodynamics and sea-level change. Currently, there are three core IGS product lines: Final, Rapid and Ultra-rapid. The Finals are issued with a latency of 13 to 20 days and are intended for applications demanding the highest accuracy, such as the International Terrestrial Reference Frame (ITRF). The Rapid products are delivered with a latency of 17 hours and are of similar quality to the Finals. The Ultra-rapid products are released four times per day, each with 3 hours latency and are intended for real-time and near real-time applications. The IGS generally aims to provide ~1 cm GNSS satellite orbits and ~1 mm terrestrial reference frame products to meet the most demanding user needs. While the goal has not yet been met, the IGS has made good overall progress. The first part of this talk will provide an introductory overview of the IGS products, along with a summary of their limiting errors. The second part will focus on the pending IGS 2nd reprocessing campaign (acc.igs.org/reprocess2.html) and the expected contribution to ITRF2013. The last part will briefly summarize challenges expected to remain after the 2nd reprocessing.

NOAA’s National Geodetic Survey began the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) program in an effort to modernize and unify vertical datums in all states and territories. As a part of this program, NGS collected aerogravity profiles over the islands of Puerto Rico and the U.S. Virgin Islands in January 2009. A Citation II aircraft was equipped with an airborne gravimeter, GPS receiver, and a GPS/Inertial unit. Absolute gravity and GPS ties were made to multiple ground sites to ensure consistency in the results. The main survey covered a region of approximately 400 km by 500 km with flight altitudes of 10,668 m (35,000ft) and with 10 km track spacing. Cross-track profiles at 40 km spacing were also collected to establish an accuracy of 1.34 mGals RMSE. In addition to the high altitude flights, two more flights were made primarily over terrestrial areas at 1,524 m (5,000 ft) to obtain higher resolution information in these regions. There were no cross-ties established for these lower altitude flights. Additionally, terrestrial surveys were also conducted to better tie ground sites and to serve as control for later analysis for available but older terrestrial and marine gravity data in the region already held by NGS. The aerogravity data were analyzed and at least internally compared to obtain the optimal results before being published on the web. In this study, the aerogravity data were compared to available global gravity models derived from satellite missions (GRACE & GOCE) to evaluate their long wavelength character (e.g., potential biases and trends). The vetted satellite-aerogravity data were then combined and used to evaluate surface data (terrestrial and marine) in the region to remove any potential systematic effects. Finally, all these data were combined into a gravimetric geoid height model and evaluated with an eye to eventual use as a GNSS-accessed vertical datum.

The mission of NOAA’s National Geodetic Survey (NGS) is to define, maintain, and provide access to the National Spatial Reference System (NSRS), the foundation for navigation, mapping, and surveying in the United States. For most of its over 200 year history, NGS has largely met its mission objectives without GIS...until now. NGS has developed a GIS toolbox that includes survey tools that create attribute-rich GIS features for GNSS and geodetic leveling networks directly from NGS software output (including OPUS-Projects), and a grid conversion tool that generates standard GIS rasters from NGS grids, such as geoid models. The GIS tools were created using the Python scripting language and are accessed through the Esri ArcToolbox; a Web-based version is also being planned. Other recent NGS GIS products include: 1) development of the online “NGS Data Explorer” for accessing published NGS geodetic control; 2) creation of the “GEOCON” tool for 3D coordinate transformations between the 2011, 2007, and HARN realizations of the North American Datum of 1983; and 3) a GIS Web interface for the 2011 national adjustment that allows users to explore, query, and export detailed results. This workshop describes these new NGS GIS products and services and shows how to use them. The new tools provide better access to the NSRS and leverage the power of GIS for display and analysis of geodetic data. By developing such tools, NGS better meets the needs of our growing and diverse customer base of surveyors, GIS practitioners, and other geospatial professionals.

The world is a dynamic environment that is ever changing and NOAA's National Geodetic Survey (NGS) is working towards a reference systems to better define elevation. The North American Vertical Datum of 1988 (NAVD 88) provided a good reference based on the best theory and technology of the day. We are continuously learning more about the effects of such things as glacial rebound, oil and water extraction subsidence and vertical effects from plate tectonics. A better understanding of the geophysics of the Earth and an evolution of positioning and remote sensing technology is driving our countries’ need to replace NAVD 88. This presentation focuses on how NGS is working to define a new vertical reference system that builds on a better understanding of the earth and is compatible with current/future technology (Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project). Doing so provides continuity throughout cartographic products.

Advances in satellite geodesy have improved survey accuracies and provided new insights into our dynamic world, while revealing problems with the official reference frame used to measure them. The North American Datum of 1983 (NAD 83) should be replaced by a more truly geocentric reference frame that accounts for tectonic plate motion. The National Geodetic Survey (NGS) will discuss the history of and modifications to NAD 83, residual plate velocities, misalignment to the International Terrestrial Reference Frame (ITRF), how a new reference frame can address these issues and provide new benefits, and offer suggestions to users that will be affected.

The mission of NOAA’s National Geodetic Survey (NGS) is to define, maintain, and provide access to the National Spatial Reference System, the foundation for navigation, mapping, and surveying in the U.S. For most of its over 200 year history, NGS met its mission objectives without GIS...until now. NGS recently developed GIS tools in Esri ArcToolbox for GPS, leveling, and grid conversion. The GPS and leveling tools create attribute-rich GIS features from NGS software output for GPS processing, survey network adjustment, and geodetic leveling. The grid conversion tool creates Esri rasters from NGS grids, such as geoid models. In addition to this toolbox, NGS created a tool for 3D coordinate transformation between the HARN, NSRS2007, and 2011 realizations of NAD 83. This presentation describes the new tools and shows how to use them for display and analysis of geodetic data, both on desktops or through the Web-based NGS Geodetic Toolkit.

The Geoid Slope Validation Survey 2011 (GSVS11) was conducted at 218 benchmarks located on a line between Corpus Christi and Austin, Texas. In the survey, long session GPS positioning of the benchmarks provides the ellipsoidal height with relative accuracy of 4 mm and the precise leveling and gravity survey provide the orthometric height with relative accuracy of 16 mm for the line length of 300 km. In addition, the astrogeodetic deflections of the vertical (DoV) are measured by the DIADEM camera with accuracy of 0.1 arcsecond that can be converted into a geoid profile with the similar accuracy, consequently providing another data set for geoid validation. The treatment of the topographic effect in the profile computation is discussed. In addition, ellipsoidal height differences between benchmarks along the line are computed from DoV and leveled height differences as a test of the DoV accuracy. Finally, all data are integrated to produce an accurate and reliable geoid profile for gravity field verification and validation.

Mario provided a wealth of knowledge, including information about those with hidden disabilities, as well as legislative reform, federal programs that make it easier to hire people with disabilities, and general tips to keep in mind when interacting or communicating with people with disabilities

The National Oceanic and Atmospheric Administration’s National Geodetic Survey (NGS) is responsible for providing the nation’s official fundamental positioning infrastructure - the National Spatial Reference System (NSRS). NSRS is the common and consistent spatial framework which allows geographic data from disparate sources to be successfully assimilated and analyzed. Global Navigation Satellite System (GNSS) technology and related developments have revolutionized NGS’ ability to provide, maintain, and deliver the NSRS; this new GNSS-centric paradigm of geodetic infrastructure continues to evolve. Part 1 – National Spatial Reference System: an Overview This presentation will provide an overview of NGS geodetic data, models, and tools, with a focus on aspects that are of particular interest to GIS practitioners and surveyors. Fundamental aspects of geodesy and the importance of accurate positioning in geospatial applications will be discussed. Topics will include a review of the history and evolution of NSRS and technical developments that have resulted in the current generation of national horizontal and vertical datums and models. The roles of the networks of passive (monumented points) and active (GNSS Continuously Operating Reference Stations (CORS)) control points will be reviewed. The NGS website (geodesy.noaa.gov) serves as a portal to a wide range of information, data, and tools that can be leveraged by most users of geospatial data. Some of these resources will be described. Part 2 – National Spatial Reference System: Future Plans NGS is currently planning substantial changes to the NSRS, which, when implemented in a decade, will appreciably and positively impact geospatial activities nationwide. This next generation NSRS will provide improved accuracy and efficiency in the nation’s positioning infrastructure through enhanced utilization of GNSS and other modern technologies. As outlined in this presentation, planned changes to the NSRS include the definition and delivery of a new geometric datum, realized through GNSS CORS, to replace the North American Datum of 1983 (NAD83). Designed to complement the new geometric datum, a new vertical/geopotential datum – based on a national gravimetric geoid and replacing the North American Vertical Datum of 1988 (NAVD88) – will also be developed and co-released. The ongoing Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project is providing the nationwide airborne gravity data required by the new vertical datum and will be described. The conditions necessitating these new datums and recommendations for the eventual user transition to them will be reviewed.

The National Oceanic and Atmospheric Administration’s National Geodetic Survey (NGS) is planning substantial changes to the National Spatial Reference System (NSRS) – the national system of latitude, longitude, elevation, and related geodetic models and tools – which, when implemented in about a decade, will positively impact surveying and mapping activities nationwide. The new NSRS will provide improved accuracy and efficiency in the nation’s positioning infrastructure through enhanced utilization of the Global Navigation Satellite System (GNSS) and other modern technologies. Planned changes to the NSRS include the definition of a new vertical datum to replace the North American Vertical Datum of 1988 (NAVD88) and the definition of a new geometric datum to replace the North American Datum of 1983 (NAD83). This presentation will review the current status of national datums and geodetic infrastructure as well as the availability of various positioning data, products and services provided by NGS. The following topics will also discussed - a description of the new datums, the need for their implementation, some outstanding issues yet to be resolved, and considerations for a smooth transition.

The National Geodetic Survey’s (NGS’s) Gravity for the Redefinition of the American Vertical Datum (GRAV-D) program will collect airborne gravity data across the entire U.S. and its holdings over the next decade. To achieve the best airborne gravity data accuracy possible, accurate aircraft positions, velocities, and accelerations are necessary for calculating the gravity corrections. So, in August 2010, NGS issued the “Kinematic GPS Processing Challenge” (hereafter called the “Challenge”) asking for kinematic positioning specialists to voluntarily process geodetic-quality L1/L2 GPS data on two GRAV-D flights. The goal of the Challenge is to directly compare the position from a variety of methods to examine the precision and accuracy of available kinematic processing methods, as well as compare the gravity results computed from each of those position solutions. This paper will focus on only the positioning results. Nineteen position solutions for each of two days of data were submitted from twelve contributors in response to the Challenge.

The Online Positioning User Service (OPUS) is a National Geodetic Survey tool that provides you with a National Spatial Reference System coordinate via email in seconds using your own GPS data file. Several notable enhancements have been implemented or are pending for OPUS. OPUS-Projects is a new option providing tools to handle GPS projects involving several sites occupied over several days. OPUS-Projects includes project visualization and management tools, enhanced processing options, and “one click” publishing for an entire project. OPUS is testing a new static processing strategy. By including more CORS at various distances and more sophisticated geophysical models, this new strategy improves the reliability of the results without sacrificing flexibility. OPUS-RS also offers a new CORS selection strategy which improves reliability and expands the regions in which this is a viable processing option. Underlying these enhancements are new CORS coordinates derived from a recently completed global GNSS network solution. This solution provides improved coordinates for all included CORS that are consistent with recognized reference systems such as the ITRF2008. These and other new developments will be described.

Since 1980 various groups have executed comparisons of absolute gravimeters for the purpose of determining the accuracy of operational meters. While the final method of processing data and estimating meter accuracy has varied from comparison to comparison, one common fact has persisted – two meters can not observe gravity at both the same time and the same place. With this simple fact in mind, and despite variations in the final method of data processing, it has always been necessary to develop an efficient observation schedule for a comparison. Such a schedule must obviously depend on the number of meters in attendance and number of observing piers available. But other factors must be considered, such as how many observations each meter is required to make, how many times a meter compares to another meter and how many times a meter compares to itself – all of which effect the conditioning of the equation system. Finding the most efficient schedule with the greatest conditioning of the equation system is a problem of optimization. The number of possible combinations for even small numbers of meters and piers grows exponentially out of computational possibility if a brute force method is used. This talk discusses an efficient solution to forming such an optimized schedule, and a fast computer program which makes use of this solution.

The techniques employed during the development of the Geoid Slope Validation Study of 2011 (GSVS 11) were adapted to modeling of regional geoid height models. Aerogravity from the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) Project was first evaluated with respect to satellite gravity field models developed from both GRACE and GOCE data to establish long wavelength consistency and remove biases in individual survey lines. In turn, the airborne and satellite gravity were then combined to evaluate surface gravity data from around 1400 separate surveys over the conterminous United States (CONUS). These surveys can span anywhere from 10's to 100's of kilometers and comprise the surface gravity database held by the U.S. National Geodetic Survey. These surface data have been used as-is in the development of previous gravimetric geoid models. With the availability of aerogravity, these surveys were examined to detect and mitigate potential biases that can create artifacts in geoid height models. About 5% of these surveys exhibit significant biases of 3-5 mGals, which equate to 10-20 cm errors in subsequent geoid height models. Given the requirement for cm-level accuracy in a future vertical datum based on geoid height models, these errors must be addressed. GSVS 11 demonstrated that it is possible to combine satellite, airborne and surface gravity to achieve cm-level accuracy over a limited locale. This study demonstrates that this can also be achieved over more regional scales. While not all of the CONUS has yet been flown by the GRAV-D Project, significant portions have been flown and those regions have been evaluated here. In the GSVS 11 study, external metrics were collected simultaneously to permit evaluation of the overall error. Such data is generally not available on a national basis, but comparisons are made with the GSVS 11 data, tidal benchmarks in combination with ocean topography models, and astrogeodetic deflection of the vertical data.

The GRAV-D (Gravity for the Redefinition of the American Vertical Datum) Project of the U.S. National Geodetic Survey plans to collect airborne gravity data across the entire U.S. and its holdings over the next decade. The goal of the project is to create a gravimetric geoid model to use as the national vertical datum by 2022. The project plan and more details are available: http://www.ngs.noaa.gov/GRAV-D GRAV-D (as of August 2013) has publicly released full-field gravity products from these high-altitude flights for >15% of the country. The full-field gravity (FFG) at altitude product is versatile because it allows the user to calculate any disturbance or anomaly that is appropriate for their application- based on any datum and height above the datum desired. This poster compares available methods of calculating gravity disturbances and assesses them for their errors across all latitudes and from zero to 11 km altitude. In the conclusions, we recommend the most accurate method for calculating disturbances. Also, before comparing two sets of gravity disturbances collected at different heights, an additional step must be taken to filter or continue the data sets until they have matching signal content.

Absolute and relative gravity measurements play an important role in the work of NOAA's National Geodetic Survey (NGS). When NGS decided to replace the US national vertical datum, the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project added a new dimension to the NGS gravity program. Airborne gravity collection would complement existing satellite and surface gravity data to allow the creation of a gravimetric geoid sufficiently accurate to form the basis of the new reference surface. To provide absolute gravity ties for the airborne surveys, initially new FG5 absolute measurements were made at existing absolute stations and relative measurements were used to transfer those measurements to excenters near the absolute mark and to the aircraft sensor height at the parking space. In 2011, NGS obtained a field-capable A10 absolute gravimeter from Micro-g LaCoste which became the basis of the support of the airborne surveys. Now A10 measurements are made at the aircraft location and transferred to sensor height. Absolute and relative gravity play other roles in GRAV-D. Comparison of surface data with new airborne collection will highlight surface surveys with bias or tilt errors and can provide enough information to repair or discard the data. We expect that areas of problem surface data may be re-measured. The GRAV-D project also plans to monitor the geoid in regions of rapid change and update the vertical datum when appropriate. Geoid change can result from glacial isostatic adjustment (GIA), tectonic change, and the massive drawdown of large scale aquifers. The NGS plan for monitoring these changes over time is still in its preliminary stages and is expected to rely primarily on the GRACE and GRACE Follow On satellite data in conjunction with models of GIA and tectonic change. We expect to make absolute measurements in areas of rapid change in order to verify model predictions. With the opportunities presented by rapid, highly accurate absolute gravimetry, we expect that GRAV-D may be affected in a number of ways. 1) Areas requiring re-measurement as a result of poor quality data or temporal change could be measured with such a new meter. With a meter capable of field measurement with observation times that are very short, surveys previously conducted only with the relative meters could be performed with the absolute meter with no loss of time and a significant increase in accuracy. 2) Regions of rapid change due to hydrological change associated with aquifers could be measured and re-measured rather quickly. Such accuracy may provide more accurate snapshots of the aquifers over time. 3) NGS conducts absolute gravity comparisons at its Table Mountain facility for validating the performance of absolute meters through their co-located operation at gravity piers. An increase in accuracy of an order of magnitude may change the entire nature of absolute meter performance evaluation.

As part of continuing efforts to improve the National Spatial Reference System (NSRS), in June 2011 NOAA's National Geodetic Survey (NGS) completed a nationwide adjustment of “passive” control (i.e., physical survey monuments). This adjustment yielded updated North American Datum of 1983 (NAD 83) coordinates on 79,677 passive stations positioned using Global Navigation Satellite System (GNSS) technology. It was accomplished through least-squares adjustments of 424,157 GNSS vectors observed between April 1983 and December 2011. The adjustment was constrained to North American Datum of 1983 (NAD 83) coordinates of 1195 NGS Continuously Operating Reference Stations (CORS). NAD 83 CORS coordinates were determined in September 2011 as part of the Multi-Year CORS Solution (MYCS) Project, and it constitutes a GNSS-based “active” control system that is the geometric foundation of the NSRS. Constraining the adjustment to the CORS optimally aligns the GNSS passive control with the active control, providing a unified reference frame to serve the Nation’s geometric positioning needs. The resulting realization gives positions at a date of January 1, 2010, and it is formally designated as NAD 83(2011/PA11/MA11) epoch 2010.00. This workshop will cover the methods, results, and challenges of performing the latest nationwide adjustment of passive control. Completion of the MYCS and national adjustment represents a significant step toward a more integrated NGS, in terms of both better positions and improved access to the NSRS. To illustrated this, affected NGS products and services will also be covered, including: 1) the new NGS Datasheet format; 2) improvements to the NGS “ADJUST” least-squares adjustment program and the “Bluebooking” process; 3) newly developed tools that convert output from NGS GPS and leveling adjustment software to GIS features; 4) the new hybrid geoid model (GEOID12A); and 5) new tools to transform positions between the High Accuracy Reference Network (HARN), NSRS2007, and 2011 realizations of NAD 83.

This presentation has three parts: 1. A discussion of the U.S. National Geodetic Survey’s National Spatial Reference System and problems with the current vertical datum (NAVD88). 2. Details about the GRAV-D (Gravity for the Redefinition of the American Vertical Datum) and its role in defining the new vertical datum by 2022. The geoid that will help define the new datum will be based on gravity data from existing satellite, terrestrial, and marine gravity sources and the new GRAV-D airborne gravity data. 3. The new reference surface will be easily accessed through GNSS and a positioning service to provide rapid orthometric heights accurate to as little as 2 cm, anywhere in the United States. The new datum and new access methods will have major impacts in professional surveying in the U.S., including a new freedom for many surveying applications from needing to access benchmarks.

The International GNSS Service (IGS) generally aims to provide ~1 cm satellite orbits and ~1 mm terrestrial frame products to meet the most demanding user needs. While the goal has not yet been met, the IGS has made good progress. The current Global Positioning System (GPS) Final orbits have accuracies better than 2.5 cm; the Rapids are of similar quality; and the near real-time parts of the Ultra-rapids have an accuracy of ~3.0 cm, while the real-time parts have an accuracy of about 5 cm. About half of the total error in the GPS orbits can be attributed to systematic time-varying rotational misalignment of the orbital frames; the other half is dominated by sub-daily tidal variations in Earth orientation. Near-field multi-path errors, anthropogenic changes at tracking stations, and the presence of uncalibrated GNSS antenna radomes at multi-technique sites continue to be a significant source of error in the terrestrial frame products. While recent model and analysis changes have reduced some errors, others will remain for the foreseeable future. This paper will summarize the current quality state of the IGS Final, Rapid and Ultra-rapid products as preparations for the next reprocessing campaign continue.

"NGS Updates" will include remarks on recent progress on OPUS, GRAV-D, Geoid Slope Validations Surveys, and Minnesota Level Network.

As part of its Ten Year Strategic Plan (2013-2023), the National Geodetic Survey (NGS) of the USA is planning to replace the North American Vertical Datum of 1988 (NAVD 88) by the year 2022. The replacement vertical datum will be defined through a gravimetric geoid model and accessed via GNSS technology, in direct contrast to the definition and access of NAVD 88, which is through passive, generally unmonitored benchmarks connected through geodetic leveling. A USA-Canada-Mexico joint effort is underway to compute a single geoid model by 2022 for the entire region, which can be adopted as the vertical datum reference surface by all countries within the area. The proposed area ranges from the North Pole to the Equator and from the Aleutian Islands (in the west) to the islands of Newfoundland (in the east). As such, the entirety of the Caribbean Sea, all of Central America, all of Hawaii, plus parts of Greenland and South America will be covered. This will allow one singular, unified vertical datum to be accessible to every country in the region, alleviating the need for island-by-island vertical datums as is currently the case. A major component of the geoid modeling effort is NGS’s GRAV-D project (Gravity for the Redefinition of the American Vertical Datum). That project has a two-fold approach: First, to collect a static, accurate “snapshot” of the entire gravity field. This is primarily being done through airborne gravity collection over the USA and its territories, as well as through improvements in and additions to terrestrial data holdings. A second, long-term effort of GRAV D is to monitor the geoid over time. This talk will discuss the prospects of improving the static gravity field holdings outside of the USA and its territories, including a discussion on existing holdings, data gaps and NGS’s desire for potential collaborations with interested countries in the region both before and after the 2022 datum change.

This presentation outlines the status and future plans of the national geometric and vertical datums and related models and tools, including the national network of GNSS Continuously Operating Reference Stations (CORS) and the related Online Positioning User Service (OPUS). It also discusses the need and reviews procedures for capturing GPS on bench mark (GPSBM) occupations for improving future geoid models, including how to use DSWorld (free software tool) for researching candidate GPSBM stations. As delivered, this presentation included some online demonstrations, which are only partially captured in the static Powerpoint slides.

Keep members of the surveying community apprised upcoming changes wrt datums as well as products and services that NGS offers.

This meeting served as the capstone for an investigation of the use of GOCE satellite data to level across the North Atlantic Ocean based on comparisons at tide gauges. This presentation focused on the use of GOCE data as a reference field for optimizing aerogravity data and, in turn, using that data to analyze surface gravity data - particularly in the Northeastern U.S. and over the Great Lakes.

The National Geodetic Survey (NGS) is the lead federal agency on the Federal Geodetic Control Subcommittee (FGCS), which is a part of the broader Federal Geographic Data Committee (FGDC). While the FGDC focuses on broader collaboration involving geospatial data, the FGCS focuses on maintaining the National Spatial Reference System (NSRS) to ensure maximum accuracy and consistency when referencing the geospatial data. NGS is a responsible for maintaining the NSRS and access to it. The NSRS is composed of a number of elements including the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88). Both of these show significant problems when viewed in the context of global observing systems such as GNSS and data from the GRACE gravity satellite mission (Tapley et al. 2005). Meter level biases and slopes are seen in NAD 83, while NAVD 88 shows similar problems with 30-50 cm regional variations. Both of these are problematic given expectation by users for centimeter-level of accuracy. NGS is moving to adopt new datums to replace NAD 83 and NAVD 88 by the end of the next decade. These changes will impact not only federal agencies but all those who rely upon the products of those agencies. Examples would include map products from the USGS, flood plain maps (FIRMettes), cadastral information at the county level, and numerous GIS applications. This also will impact commercial and engineering operations that rely upon precise positioning and the local gravity field variations including shipping and port operations, pipelines, and surveys. NGS intends to replace NAD 83 with a new ellipsoidal datum more consistent with more recent reference frameworks (e.g., ITRF05). More significantly, NAVD 88 will be replaced by a gravimetric geoid height model. This model will work in conjunction with the new ellipsoidal datum to provide consistent, cm-level accurate, GNSS-derived orthometric heights. These heights will be capable of being transformed to express geopotential numbers to provide dynamic or other types of heights. The new vertical datum will be developed through the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project (Smith 2007). This project will collect gravity field information from numerous sources and spectrally meld them into a seamless whole.

NOAA's National Geodetic Survey (NGS) is tasked by Congress to establish and maintain the National Spatial Reference System, which includes latitude, longitude, and elevations for the nation. NAVD 88 (North American Vertical Datum of 1988) was the last main effort to establish a reference for orthometrics heights. NAVD 88 was determined as a result of a massive leveling campaign across the nation. Recent satellite measurements show that NAVD 88 does not well match the true surface of zero elevation in the country (despite being very internally consistent). NGS has decided to replace NAVD 88 with a newer, more accurate vertical datum through a project called GRAV-D: Gravity for the Redefinition of the American Vertical Datum. The final outcome of GRAV-D will be new vertical datum, slated for release in 2022. You may think, that's 8 years away, so why should I be concerned? The talk will focus on the changes to the surveyor community expected to result from this new datum.

This presentation outlines the status and future plans of the National Geodetic Survey’s (NGS) national geometric and vertical datums and related models and tools, including the national network of GNSS Continuously Operating Reference Stations (CORS) and the related Online Positioning User Service (OPUS), with a focus on the NGS Height Modernization Program. Also discussed will be the need and procedures for capturing GPS on bench mark (GPSBM) occupations for improving future hybrid geoid models, including how to use DSWorld for researching candidate GPSBM stations and OPUS for sharing user results with NGS and the public. The live presentation will included demonstrations of DSWorld and OPUS, as applied to the GPSBM effort.

IGS tracking stations are most effective when all possible sources of data noise and errors are mitigated. Multipath remains a source of unmitigated and unmodeled error, even when the best quality geodetic antennas are utilized. The typical geodetic antenna is designed to be easily shipped and transported, so it can be deployed in campaign GNSS studies. IGS tracking stations are unique because, to maintain time series integrity, their antennas are typically used for years (or decades!) without transport or uninstall. To meet the high data quality needs of IGS tracking stations, if antenna size and weight were not a limiting factor, is it possible to design and build an antenna which can mitigate multipath and additional unmodeled noise beyond the typical geodetic antenna currently in use at IGS stations? To meet this challenge, Topcon has designed and built two prototypes of a large impedance ground plane GNSS antenna, which we refer to as “BigAnt” in this paper. The antenna ground plane is 3 meters in diameter. Topcon’s initial results show that BigAnt has better multipath rejection above 10 degrees and lower systematic noise in double difference phase data and kinematic positions, compared to a conventional geodetic chokering. But what does this mean for positioning quality at IGS tracking stations? To answer this question, Topcon and the US National Geodetic Survey (NGS) have partnered to collect multiple months of data with both BigAnt and a standard geodetic chokering. The two stations are of equivalent height above a large flat field, and are about 50 m apart. Data collection began 3 March 2014 and is ongoing. We present preliminary results from this field campaign. PPP time series from BigAnt and the chokering are discussed in depth, as well as statistics for postfit residuals, solution sigmas, and single station ambiguity resolution. To directly assess data quality, we also discuss teqc QC metrics and the spectral content of SNR data (a proxy for phase multipath). Finally, we include a relative field calibration of BigAnt and discuss the effect of this calibration on PPP results.

GeoCue Group is pleased to present “A Conversation with the National Geodetic Survey.” The National Geodetic Survey’s (NGS) mission is to “define, maintain and provide access to the National Spatial Reference System to meet our nation's economic, social, and environmental needs." In simple terms, the NGS is, for the United States and its territories, ground zero for precise positioning information. From defining the nation’s spatial reference systems to free on-line services for survey position refinement, the NGS provides research and services vital to the surveying, civil engineering and GIS interests of the USA. This topic is presented by Mr. Brett Howe, the Geodetic Services Division (GSD) Chief for the National Geodetic Survey of the National Ocean Service (NOS)/ National Oceanic and Atmospheric Administration (NOAA).

IGS tracking stations are most effective when all possible sources of data noise and errors are mitigated. Multipath remains a source of unmitigated and unmodeled error, even when the best quality geodetic antennas are utilized. The typical geodetic antenna is designed to be easily shipped and transported, so it can be deployed in campaign GNSS studies. IGS tracking stations are unique because, to maintain time series integrity, their antennas are typically used for years (or decades!) without transport or uninstall. To meet the high data quality needs of IGS tracking stations, if antenna size and weight were not a limiting factor, is it possible to design and build an antenna which can mitigate multipath and additional unmodeled noise beyond the typical geodetic antenna currently in use at IGS stations? To meet this challenge, Topcon has designed and built two prototypes of a large impedance ground plane GNSS antenna, which we refer to as “BigAnt” in this paper. The antenna ground plane is 3 meters in diameter. Topcon’s initial results show that BigAnt has better multipath rejection above 10 degrees and lower systematic noise in double difference phase data and kinematic positions, compared to a conventional geodetic chokering. But what does this mean for positioning quality at IGS tracking stations? To answer this question, Topcon and the US National Geodetic Survey (NGS) have partnered to collect multiple months of data with both BigAnt and a standard geodetic chokering. The two stations are of equivalent height above a large flat field, and are about 50 m apart. Data collection began 3 March 2014 and is ongoing. We present preliminary results from this field campaign. PPP time series from BigAnt and the chokering are discussed in depth, as well as statistics for postfit residuals, solution sigmas, and single station ambiguity resolution. To directly assess data quality, we also discuss teqc QC metrics and the spectral content of SNR data (a proxy for phase multipath). Finally, we include a relative field calibration of BigAnt and discuss the effect of this calibration on PPP results.

Since 1994, NGS has computed relative antenna calibrations for more than 350 antenna models used by NGS customers and geodetic networks worldwide. In a "relative" calibration, the antenna under test is calibrated relative to a standard reference antenna, the AOA D/M_T chokering. The majority of NGS calibrations have been made publicly available at the web site www.ngs.noaa.gov/ANTCAL as well as via the NGS master calibrations file ant_info.003. "Absolute" antenna calibrations, where the antenna under test is calibrated independent of any reference antenna, began in the mid-2000s at Geo++ and other institutions. Soon thereafter (2008), the International GNSS Service (IGS) initiated a geodetic community movement away from relative calibrations and toward absolute calibrations as the defacto standard. The IGS now distributes a catalog of absolute calibrations taken from several institutions, distributed as the IGS master calibrations file igs08.atx. The competing methods and files have raised many questions about when it is or is not valid to process a geodetic network using a combination of relative and absolute calibrations, and if/when it is valid to combine the NGS and IGS catalogs. Therefore, in this study, we compare the NGS catalog of relative calibrations against the IGS catalog of absolute calibrations. As of September 2013, there were 77 antenna+radome combinations which are common to both the NGS relative and IGS absolute catalogs, spanning 16 years of testing (1997 to present). 50 different antenna models and 8 manufacturers are represented in the study sample. We apply the widely-accepted standard method for converting relative to absolute, then difference the calibrations. Various statistics describe the observed differences between phase center offset (PCO), phase center variation (PCV), and full phase center correction (PCC). We analyze these differences in the context of time, to understand potential calibration technique changes over time. We also view the differences through the lens of antenna type (e.g. patch antenna, chokering, integrated receiver/antenna unit) to understand how the calibration technique and/or nearfield test environment may affect the calibration values.