GPS World

Tag: NGS

  • Plate tectonics and NGS’s new NSRS terrestrial reference frames

    Plate tectonics and NGS’s new NSRS terrestrial reference frames

    The adoption of the new, modernized National Spatial Reference System (NSRS) is rapidly approaching, with official implementation now expected in the first quarter of 2027.

    One of the most common questions I receive during presentations is: How will the National Geodetic Survey (NGS) account for plate tectonics in the modernized NSRS, and what does that mean for my geospatial products and services?

    First, I have some very sad news to share.

    Dr. Chris Pearson
    Dr. Chris Pearson

    Our friend and colleague, Dr. Chris Pearson, unexpectedly passed away while in Cape Town attending the May 2026 International Federation of Surveyors (FIG) conference. At the time, he was serving as a Geodetic Advisor for Trimble and as co-chair of FIG Commission 5.2.

    Chris previously worked for the National Geodetic Survey (NGS) as a Geodetic Advisor, where he played a key role in developing the comprehensive block model of crustal deformation — widely known as HTDP — across the western United States, including Alaska.

    He was an active and respected member of several professional organizations and will be greatly missed by the entire geodetic and surveying community.

    Now, let’s discuss how the National Geodetic Survey (NGS) will handle plate tectonics in the modernized National Spatial Reference System (NSRS) and what this will mean for users’ geospatial products and services.

    Map of tectonic plates (Image: Dave Zilkoski)

    Plate tectonics is the scientific theory that describes how Earth’s outer shell, known as the lithosphere, is divided into large, rigid pieces called tectonic plates. These plates float atop the hotter, more ductile rock in the mantle below and move very slowly — roughly at the same rate as your fingernails grow, about 1 to 10 centimeters per year.

    So why does plate tectonics matter for geodetic coordinates? Because the most significant geological activity — including earthquakes, volcanic eruptions, and crustal deformation — occurs primarily at the boundaries where these plates interact.

    My last newsletter highlighted several activities by the North Carolina 2022 Reference Frame Working Group (NC RFWG) that are addressing this issue and other challenges related to the implementation of the new NSRS.

    During my presentations on the modernized NSRS, I always show the National Geodetic Survey (NGS) maps that illustrate the approximate horizontal and vertical changes expected when the new Terrestrial Reference Frames (TRFs) are adopted, with coordinates referenced to epoch 2020.00. These maps provide a high-level (“30,000-foot”) overview of the anticipated changes. However, they do not include the level of detail that many users are looking for.

    Participants at these seminars and meetings consistently want to know the expected coordinate differences for their specific state or local region, and how the time-dependent components will impact their work.

    Most geospatial users now understand that International Terrestrial Reference Frame (ITRF) coordinates include a velocity component caused by tectonic plate movement. To manage these changing coordinates, the National Geodetic Survey (NGS) plans to incorporate time-dependent modeling. NGS has developed two key models — EPP2022 and IFDM2022 — to make time-dependent geodetic control practical and usable.

    • EPP2022 (Euler Pole Parameters) describes the rigid rotation of tectonic plates.
    • IFDM2022 (Intra-Frame Deformation Model) computes the internal deformation and drift within a tectonic plate.

    As shown in the figure below, the NOAA CORS Network station COLA in Columbia, South Carolina — located on the North American Plate — is moving at approximately 0.05 feet (14 mm) per year.

    This velocity is provided on the published ITRF2020 position and velocity data for the station  (NGS CORS Position and Velocity Sheet for COLA).  As a result, a surveyor working in June 2026 would observe a shift of about 0.3 feet in the ITRF2020 horizontal coordinates compared to the 2020.00 reference epoch, solely due to tectonic plate motion.

    Motion due to plate movement (rates per year) – based on ITRF2020 velocity rates

    Image: Dave Zilkoski
    (Image: Dave Zilkoski)

    The National Geodetic Survey (NGS) provides detailed information for all NOAA CORS Network (NCN) stations on the NGS NCN Station Pages. 

    In the section titled “Coordinates and Velocities”, simply click the Position and Velocity button to view the station’s ITRF2020 coordinates and velocities (referenced to epoch 2020.00), as well as the NAD 83 (2011) coordinates and velocities (referenced to epoch 2010.00).

    NGS CORS position and velocity sheet for COLA

    NGS CORS position and velocity sheet for COLA

    So, what does this mean for users?

    As previously mentioned, the National Geodetic Survey (NGS) is expected to adopt the new modernized NSRS in the first quarter of 2027. The figure below shows the change in ITRF2020 coordinate values between epoch 2020.00 and 2027.00 for NOAA CORS Network (NCN) stations in South Carolina. This shift of approximately 0.33 feet (10 cm) is the result of seven years of tectonic plate motion.

    ITRF2020, Epoch 2020 to ITRF2020, Epoch 2027 (units ift)

    ITRF2020, Epoch 2020 to ITRF2020, Epoch 2027 (units ift) Image: Dave Zilkoski
    Image: Dave Zilkoski

    That said, what will the change in NATRF2022 coordinate values be between epoch 2020.00 and 2027.00?

    This is where NGS’s EPP2022 and IFDM2022 models become essential. My February 2022 and July 2024 GPS World newsletters discussed the Euler Pole Parameters (EPP) process in detail.

    The Beta NATRF2022 website provides the Euler Pole Parameters (EPP) needed to define the relationship between ITRF2020 and the new NATRF2022 frames for the North American, Caribbean, Pacific, and Mariana plates, as outlined in NGS’s Blueprint Part 1 document. The values in the table have proven especially useful to programmers developing and testing their software.

    Beta Values for EPP

    Beta Values for EPP (Image: NGS)
    (Image: NGS)

    As stated in Blueprint Part 1, the National Geodetic Survey (NGS) will define the official relationship between ITRF2020 and the four NSRS Terrestrial Reference Frames (TRFs) through Equation 59. This equation uses the rotation matrix provided in Equation 58, which results in Equation 60.

    See the box titled “Official Relationship Between ITRF2020 and the Four NSRS TRFs” for the equations.

    Official relationship between ITRF2020 and the four NSRS TRFs

    Official relationship between ITRF2020 and the four NSRS TRFs (Image: NGS Blueprint pt. 1)
    (Image: NGS Blueprint pt. 1)

    So, what does this mean for surveyors?

    The primary purpose of the EPP2022 model is to remove the rigid tectonic plate motion from the coordinates. After applying the EPP2022 model to the ITRF2020 coordinates at epoch 2027.00, the resulting NATRF2022 horizontal coordinates for station COLA (epoch 2027.00) will change by only 0.04 feet (12 mm).

    EPP applied

    NATRF2022, Epoch 2020 to NATRF2022, Epoch 2027 in SC (units ift)

    Image: Dave Zilkoski
    Image: Dave Zilkoski

    As shown in the figure, the EPP2022 model removes most of the horizontal movement caused by seven years of tectonic plate motion — reducing it to just 0.04 feet (1.2 cm) at station COLA. In other words, the EPP model effectively removes the vast majority of plate tectonic effects.

    Additionally, the plot shows that the relative horizontal differences between nearby marks are very small — typically less than 0.01 feet (0.3 cm).

    As previously mentioned, the NGS maps provide a high-level (“30,000-foot”) view of the expected changes between the current NSRS and the new modernized NSRS. So, what are the anticipated differences between NAD 83 (2011) and NATRF2022 specifically in South Carolina?

    The figures below illustrate the differences in both horizontal position and ellipsoid heights between NAD 83 (2011) and NATRF2022 coordinates across South Carolina.

    NAD83 (2011), Epoch 2010 to NATRF2022, Epoch 2020 Horizontal Changes in SC (Units ift)

    NAD83 (2011), Epoch 2010 to NATRF2022, Epoch 2020 Ellipsoid Height Changes in SC (Units ift)

    The magnitude of these changes varies depending on your location. To illustrate this, I’ve provided two additional examples: one for Iowa and one for Washington State. As the plots clearly show, the differences in these states are noticeably different from those depicted for South Carolina.

    NAD83 (2011), Epoch 2010 to NATRF2022, Epoch 2020 Horizontal Changes (Units ift)

    That said, the differences between NATRF2022 at epoch 2020.00 and epoch 2027.00 in Iowa and Washington State — after applying the EPP2022 model — are very similar to the values shown for South Carolina.

    However, readers should note that the differences in Washington State increase as you move toward the coast. This is because the area lies near the boundary between the North American Plate and the Pacific Plate. The Juan de Fuca Plate, a small microplate in the eastern North Pacific, is also actively involved in this region.

    (See the box titled “Juan de Fuca Plate.”)

    NATRF2022, Epoch 2020 to NATRF2022, Epoch 2027 (units ift)EPP Applied

    Juan de Fuca Plate

    The Juan de Fuca plate or Juan de Fuca microplate is a small oceanic tectonic plate (microplate) generated from the Juan de Fuca Ridge that is subducting beneath the northerly portion of the western side of the North American plate at the Cascadia subduction zone.

    Image: Dave Zilkoski
    Image: Dave Zilkoski

    What about orthometric height changes in the new NSRS?

    As an example, the orthometric height differences between NAPGD 2022 and NAVD 88 in South Carolina are expected to range from approximately -0.8 feet to -1.3 feet.

    Difference between NAPGD2022 and NAVD 88 (Units ift) in S.C.

    Image: Dave Zilkoski
    Image: Dave Zilkoski

    The differences between NAPGD 2022 and NAVD 88 vary significantly depending on your location. The figures below illustrate these orthometric height differences for Iowa and Washington State as examples.

    Difference between NAPGD2022 and NAVD 88 (Units ift)

    The new NSRS will use a gravimetric geoid (GEOID2022) rather than a hybrid geoid (GEOID18) to compute GNSS-derived orthometric heights.

    During my presentations, I always remind participants that a hybrid geoid is not a “true” geoid. It is simply a transformation model that converts ellipsoid heights in one reference frame to orthometric heights in a specific vertical datum. Specifically, GEOID18 is a transformation tool that allows users to derive NAVD 88 orthometric heights from NAD 83 (2011), epoch 2010 ellipsoid heights.

    The figure below shows the differences between the gravimetric geoid model GEOID2022 and the hybrid geoid model GEOID18.

    Important note: Users cannot use GEOID18 with NATRF2022 ellipsoid heights to obtain NAVD 88 orthometric heights. Instead, GEOID2022 must be used with NATRF2022 ellipsoid heights to compute orthometric heights in the new vertical datum, NAPGD 2022.

    Differences between GEOID2022 and GEOID18 in SC (Units ift)

    As noted at the outset of this newsletter, the transition to the modernized National Spatial Reference System (NSRS) is rapidly approaching, with official implementation scheduled for the first quarter of 2027.

    The National Geodetic Survey (NGS) released the following announcement on May 28, 2026:

    Public Testing Period Ends for Key NSRS Modernization Products

    NGS has declared the following products stable and ready for implementation planning and integration activities ahead of the official release:

    • North American-Pacific Geopotential Datum of 2022 (NAPGD2022)
    • New Terrestrial Reference Frames of 2022:
      • North America (NATRF2022)
      • Pacific (PATRF2022)
      • Caribbean (CATRF2022)
      • Mariana (MATRF2022)
    • State Plane Coordinate System of 2022 (SPCS2022)

    Additional modernization products, including NCAT, OPUS, and the Data Delivery System, are scheduled for release later in 2026.

    NGS news

    Public testing period ends on specific NSRS modernization products

    Image: NOAA

    Image: NOAA

    This newsletter highlighted the role of the EPP2022 model in accounting for plate tectonics and illustrated the anticipated local differences between the current National Spatial Reference System (NSRS) and the upcoming modernized version.

    Future editions will continue to explore additional NGS Beta products as they are released later in 2026.

  • Update on NC 2022 reference frame working group: Preparing information for NC geospatial providers and users

    Update on NC 2022 reference frame working group: Preparing information for NC geospatial providers and users

    In my October 2025 GPS World Newsletter, I highlighted professional societies forming working groups for the new NSRS — the National Society of Surveyors (NSPS), the American Society of Photogrammetry and Remote Sensing (ASPRS), and the American Association for Geodetic Surveyor (AAGS). Under Gary Thompson’s leadership, the North Carolina Geodetic Survey also established the North Carolina 2022 Reference Frame Working Group (NC RFWG), which includes representatives from NC agencies that produce or use geospatial products and services. This newsletter spotlights several NC RFWG activities to inform and assist other agencies and working groups.

    As noted in my previous newsletter, NC RFWG agencies are proactively conducting self-assessments of their needs and processes to identify challenges and opportunities early, enabling a smooth transition and sustained operational efficiency. The working group meets monthly to review progress on activities.

    One key task of the working group was to develop a short online questionnaire. The goal was to open a dialogue with geospatial professionals and better understand their readiness for the upcoming modernization of the National Spatial Reference System (NSRS).

    The questionnaire was designed to address the following key questions:

    • Are you prepared to implement the new NSRS once the National Geodetic Survey (NGS) officially adopts it?
    • Do you have the necessary tools and resources in place to ensure a smooth transition?
    • Has your organization established a timeline for transitioning to the modernized NSRS?
    • What concerns do you have regarding the transition to the new NSRS?

    The section titled “Introduction of North Carolina Questionnaire” explains the purpose and background of the survey, while the section titled “North Carolina Online Questions” presents the list of questions included in the questionnaire.

    Introduction of the North Carolina Questionnaire

    This questionnaire seeks stakeholder input on the upcoming modernization of the National Spatial Reference System (NSRS). Your feedback is welcome on the proposed questions, as well as any concerns about the datum transition, tools (such as updated NCAT, OPUS, and SPCS2022), data transformation strategies, workflow impacts, and preparation needs.

    The National Geodetic Survey (NGS) is replacing the North American Datum of 1983 and the North American Vertical Datum of 1988 with new plate-fixed terrestrial reference frames (NATRF2022, PATRF2022, CATRF2022, and MATRF2022) tied to the International Terrestrial Reference Frame 2020, along with the new vertical datum, the North American-Pacific Geopotential Datum of 2022.

    In spring 2027, new horizontal and vertical datums will be implemented:

    Horizontal

    • North American Terrestrial Reference Frame (NATRF2022)
    • Replaces the North American Datum of 1983 (2011)

    Vertical

    • North American-Pacific Geopotential Datum of 2022 (NAPGD2022)
    • Replaces North American Vertical Datum of 1988

    Units

    • 14B NCAC 03 .0602 REQUIRED FOOT CONVERSION

    North Carolina Online Questions

    The section titled “Results of North Carolina Online Questionnaire” summarizes the survey responses collected as of April 27, 2026.

    [Note: NCPMA refers to the North Carolina Property Mappers Association, and LGUC refers to the North Carolina Local Government Committee.]

    Results of the North Carolina Online Questionnaire

    (April 27, 2026)

    This questionnaire solicited input from the North Carolina Property Mappers Association (NC PMA), the North Carolina Geographic Information Coordinating Council (GICC), and the North Carolina Local Government Committee (LGC). Although focused on North Carolina, the results may benefit other working groups. The NC working group is reviewing all feedback—especially regarding the Spring 2027 datum change—and will develop materials to address it.

    In addition to the questionnaire, the working group prepared a short guidance document on the new reference frames for local governments and state agencies. It outlines how to prepare for the 2027 datum change and covers:

    • Preliminary steps for transitioning when NGS and North Carolina officially adopt the new datums in 2027.
    • Actions users can take now to ready NSRS‑referenced data for the modernized NSRS and the shift from U.S. Survey Foot/International Foot.
    • Estimated coordinate changes with the 2027 adoption of:
      • North American Terrestrial Reference Frame (NATRF2022)
      • North American-Pacific Geopotential Datum of 2022 (NAPGD2022)
      • New national geoid model (Geoid2022)
      • North Carolina State Plane Coordinate System of 2022 (SPCS2022)
    • Current NC statewide digital orthoimagery acquisition cycle and statewide lidar collection schedule.
    • How the NC CORS and Real-Time Network (RTN) will support the modernized NSRS.
    • Web links to more detailed resources.


    The working group is developing a case study on preparing a FEMA Elevation Certificate using the modernized NSRS (NATRF2022 and NAPGD2022). It will be featured in upcoming newsletters. The North Carolina Geodetic Survey will host the materials on its website, and I’ll share the public link once it’s available.

  • NGS presents the latest NSRS news at Geo Week 2026

    NGS presents the latest NSRS news at Geo Week 2026

    In my January 2026 GPS World newsletter, I noted that the National Geodetic Survey (NGS) convened the Federal Geodetic Control Subcommittee (FGCS) meeting with federal geospatial agencies to boost awareness and align efforts on National Spatial Reference System (NSRS) Modernization government-wide. Key steps include cultivating internal champions to champion the initiative, distilling complex topics for clear leadership briefings, and bringing together agencies, partners, and industry to collaboratively shape solutions. I also highlighted that on Feb. 17-18, NGS staff would be participating in Geo Week 2026 in Denver to engage geospatial product and service users and further coordinate on the modernization. NGS gave several presentations during GeoWeek that addressed many of my questions on the new modernized NSRS. This newsletter will highlight some of NGS’s presentations.

    First, a special shout-out to my dear friend and former colleague, Juliana Blackwell, retired Director of the National Geodetic Survey. NOAA’s Table Mountain Gravity Observatory in Boulder, Colorado — long known for its absolute gravity work — has been officially renamed the J. P. Blackwell Gravity Observatory. This well-earned tribute honors her outstanding dedication and visionary leadership at NGS. Congratulations, Juliana!

    J. P. Blackwell Gravity Observatory. (Photo: NGS)
    J. P. Blackwell Gravity Observatory. (Photo: NGS)
    J. P. Blackwell Gravity Observatory. (Photo: NGS)
    J. P. Blackwell Gravity Observatory. (Photo: NGS)
    J. P. Blackwell Gravity Observatory. (Photo: NGS)
    J. P. Blackwell Gravity Observatory. (Photo: NGS)

    NGS employees participated in the following sessions and meetings during GeoWeek 2026:

    • ASPRS NSRS Modernization Working Group Meeting
    • NSRS Modernization — The Latest Technical Updates
    • Preparing to Put the Modernized National Spatial Reference System into Practice
    • Roundtable — NSRS Modernization and Professional Societies

    As President of the American Association for Geodetic Surveying (AAGS), I participated in the session titled “Roundtable – NSRS Modernization and Professional Societies.” Dana J Caccamise II, NGS regional geodetic advisor, opened our session by describing the NGS Modernization Engagement Plan and Progress.  As I mentioned last month, Dana should get an award for the material he has prepared and for his work assisting agencies and professional organizations in preparing for the new NSRS. I highlighted Caccamise’s work in my October 2025 GPS World newsletter.

    All the NGS sessions provided the latest information on activities associated with NGS’s NSRS Modernization. Here are the specific questions I had going into the session, along with the clear answers provided by NGS personnel during their presentations and the follow-up Q&A:

    What NGS products and services will be available when federal agencies officially adopt the new NSRS?

    When the modernized NSRS is officially adopted (following FGCS approval and the transition to it becoming “the NSRS”), NGS will make available a full suite of updated tools, data access points, and services built around the new reference frames (e.g., NATRF2022 and variants), the North American-Pacific Geopotential Datum of 2022 (NAPGD2022), the State Plane Coordinate System of 2022 (SPCS2022), and associated geopotential models like GEOID2022. Key products expected to be operational and official include:

    • NCAT
    • NGS Maps
    • Geodetic Station Page
      • CORS
    • Geodetic Mark Page
      • Passive Marks
    • OPUS–Static 5.2
    • OPUS-Share

    What NGS products and services will NOT be available when federal agencies officially adopt the new NSRS?

    Upon official adoption of the modernized NSRS — after FGCS approval and the shift to the new system becoming “the NSRS” — several current products and services will no longer be part of the official modernized NSRS or will be discontinued in their present form. Key items not included or no longer supported in the modernized NSRS release include:

    • OPUS Projects 5 will not be supported
      • OPUS-Rapid Static (OPUS-RS) will not be supported (modernized OPUS-Static 5.2 is expected to handle a broader range of observations)
      • OPUS 6.0 and OPUS 6.1 will not be available

    What GNSS data will be included in the first iteration of the computation of Reference Epoch Coordinates (REC) for marks?

    At Geo Week 2026, NGS stated that its plans include providing Reference Epoch Coordinates (RECs) for certain legacy GNSS projects. Specifically, this includes:

    • GPS projects that were originally processed and published under the NAD 83 (2011) realization, and
    • Other GNSS projects will be officially published by NGS through the end of 2025\

    After the first iteration of Reference Epoch Coordinates, is NGS planning to perform future adjustments to determine REC and SEC of new marks? If so, what process will be used to establish RECs on new marks?

    Yes, NGS plans include performing future adjustments to compute Reference Epoch Coordinates (REC) for new marks. However, at this time, no final decision has been made on how often this will be performed.

    Has NGS changed how users need to submit data to incorporate leveling data into NAPDG2022?

    Yes, NGS has introduced changes to better integrate leveling data (differential height differences) into the modernized NSRS for computing orthometric Reference Epoch Coordinates (RECs) in NAPGD2022 (epoch 2020.00).

    As documented in Blueprint Document 3, when performing leveling projects, users will also be required to occupy a number of primary marks with GNSS.

    OPUS 6.1 is built for future expansion to support other geodetic measurements (classical, leveling)-no timeframe was given for this.

    Is NGS planning to officially adopt the new NSRS before users can submit data to NGS for technical review and publication in the NGS database?

    Yes, that is what NGS is saying at this moment (February 2026). OPUS Project 5 will not be supported and OPUS 6.1 will not be operational when the new NSRS is officially adopted.NGS is working on the OPUS 6 application and is trying to “minimize any gap in service.”

    Is NGS recommending using the OPUS-Share utility until users can submit data to NGS for technical review and publication in NGS database?

    Yes, that is what NGS is recommending at this moment (February 2026). 

    This is also stated in NGS’s Track Our Progress Webpage.

    OPUS-Projects 5 will not be included in the modernized NSRS. Instead, NGS will focus on both developing an improved software suite for OPUS, known as OPUS 6.0 and OPUS 6.1, and minimizing any gap in service in which the current OPUS-Projects functionality is not available for users to organize, process, adjust, and submit high-accuracy GPS surveys for use by NGS in expanding and improving the NSRS. As noted above, OPUS-Share will remain available as a means to submit data to NGS.

    When will OPUS 6.1 be available for users to submit data to NGS for technical review and publication in NGS database?  Is it weeks away, months away, or years away?

    NGS has not announced an official completion or release date for OPUS 6.0 and OPUS 6.1. However, they have indicated that active development is underway on this enhanced OPUS tool suite.  It’s not imminent— meaning not expected within several months—but it’s also not a distant, multi-year project.

    NGS is working on the application and is trying to “minimize any gap in service.”

    The NGS’s Track Our Progress Webpage states:

    “OPUS-Projects 5 will not be included in the modernized NSRS. Instead, NGS will focus on both developing an improved software suite for OPUS, known as OPUS 6, and minimizing any gap in service in which the current OPUS-Projects functionality is not available for users to organize, process, adjust, and submit high-accuracy GPS surveys for use by NGS in expanding and improving the NSRS. As noted above, OPUS-Share will remain available as a means to submit data to NGS.”

    What’s the cut-off date for users to submit projects via OPUS Project 5 so the data can be part of future computations of RECs?

    Current OPUS-Projects 5 is going to be supported until adoption of the new NSRS, with a deadline announced at least 6 months in advance.

    The NGS’s Track Our Progress Webpage states

    “Note: the current OPUS Projects 5 software will be supported until the modernized system is adopted, and a deadline for OPUS-Projects users to submit their surveys for publication will be announced with at least six months’ notice.”

    In the session “NSRS Modernization – The Latest Technical Updates,” the National Geodetic Survey (NGS) presented slides detailing the status and upcoming tasks for the modernized National Spatial Reference System (NSRS).  Key highlights from the presentation are summarized below.

    For the source of these slides and additional context, refer to the “Updates from the National Geodetic Survey at GeoWeek 2026” box.  NGS posts their presentations at here: https://geodesy.noaa.gov/web/science_edu/presentations_library/.

    Updates from the National Geodetic Survey at GeoWeek 2026

    (Selected Slides from the following presentations)

    • 2026 GeoWeek – NSRS Modernization – The Latest Technical Updates: The Why and How of NSRS mod – February 17, 2026 – Dru Smith
    • 2026 GeoWeek – Managing Modernization Rollout – February 17, 2026 – Seth Pollack
    • 106th Wyoming Engineering and Surveying (WES) Society Conference – February 5, 2026 – Brian Shaw
    • 2026 GeoWeek – Modernized Tools – February 17, 2026 – Brian Shaw

    2026 GeoWeek –   Updates to OPUS for Accessing the Modernized NSRS – February 17, 2026 – Dan Gillins

    During Dru Smith’s presentation, he mentioned what will be included in the first iteration of the computation of Reference Epoch Coordinates (REC) for marks. The slide states that more than 150,000 geometric (XYZ) coordinates and 1 million geopotential coordinates (that is, orthometric heights) will get reference epoch coordinates (REC), epoch 2020.00.  These will include data from NGS Integrated Database and from the OPUS Share database.

    First Reference Epoch Coordinates (REC). (Presented at GeoWeek 2026)
    First Reference Epoch Coordinates (REC). (Presented at GeoWeek 2026)
    First Reference Epoch Coordinates (REC). (Presented at 106th WES Society Conference)
    First Reference Epoch Coordinates (REC). (Presented at 106th WES Society Conference)

    In the GeoWeek 2026 presentation by Seth Pollack (from NOAA’s National Geodetic Survey), a slide outlined the NSRS modernization timeline.

    As detailed in the slide and consistent with NGS’s official rollout plan:

    • Beta products are currently being released incrementally on the beta site for public testing and feedback. This phased rollout began with initial beta releases in 2025 (following alpha in 2024) and continues through 2026, covering key components such as NAPGD2022, GEOID2022, SPCS2022, enhanced NCAT transformation tools, OPUS-Static updates, and forthcoming Data Delivery System features.
      • Each beta component, once released, undergoes public testing and stakeholder feedback, with overall testing continuing for at least 6 months after the final component is made available on the beta site.
    • Following sufficient testing—once all components appear stable and NGS has incorporated feedback—the Federal Geodetic Control Subcommittee (FGCS) will vote to recommend approval of the modernized NSRS. This vote is anticipated in late 2026 or early 2027.
    • Upon FGCS approval (and subsequent Federal Geographic Data Committee (FGDC) endorsement), NGS will probably publish a Federal Register Notice announcing the adoption.  At that point, the modernized NSRS becomes the official National Spatial Reference System, replacing the legacy system (NAD 83 realizations, NAVD 88, etc.).
      • While earlier NGS documentation targeted adoption likely in mid-to-late 2026 (post-FGCS vote), recent updates from GeoWeek 2026 sessions and related reports indicate the full official adoption and transition may extend into the first part of 2027, accounting for final testing, FGCS/FGDC processes, Federal Register steps, and a smooth handover to avoid disruptions.
    • The current NSRS remains official throughout this period. Users are encouraged to test beta products now and provide feedback to help refine the system.
    NSRS Modernization Timeline. (Presented at GeoWeek 2026)
    NSRS Modernization Timeline. (Presented at GeoWeek 2026)

    Brian Shaw, NGS’s expert on GIS products and services, presented key updates on how users will access geodetic data in the modernized National Spatial Reference System (NSRS).

    He emphasized the introduction of a revamped Data Delivery System (DDS), which includes:

    • Geodetic Mark Pages — for passive marks. These replace the current ASCII-text datasheets with modernized, user-friendly pages featuring updated Reference Epoch Coordinates (RECs), integrated photos, graphics, maps, project details, and easier navigation.
    • Geodetic Station Pages — for active stations like those in the NOAA CORS Network (NCN). These provide updated versions of existing CORS pages, including modernized coordinate functions (e.g., Coordinate Functions or time-dependent positioning info) aligned with the new reference frames (NATRF2022, etc.).
    • Additionally, Shaw highlighted a new interface for the NGS Map (the interactive web map application), serving as an enhanced landing page within the DDS. This updated “NGS Map” (replacing or evolving the current version at https://noaa.maps.arcgis.com/apps/webappviewer/index.html?id=190385f9aadb4cf1b0dd8759893032db ) will provide better access to geodetic control data, CORS stations, and other layers, improving visualization and querying for surveyors, GIS professionals, and the public.
    • These changes are part of the broader DDS rollout, currently pending beta release (as of February 2026), aimed at making data more accessible, visually rich, and compatible with the modernized NSRS components (e.g., NATRF2022, NAPGD2022, SPCS2022). The DDS landing page will consolidate access, moving away from legacy datasheet formats toward dynamic, web-based delivery.
    Accessing Data from NGS. (Presented at GeoWeek 2026)
    Accessing Data from NGS. (Presented at GeoWeek 2026)
    Accessing Data from NGS. (Presented at GeoWeek 2026)
    Accessing Data from NGS. (Presented at GeoWeek 2026)
    Accessing Data from NGS. (Presented at GeoWeek 2026)
    Accessing Data from NGS. (Presented at GeoWeek 2026)

    During Dan Gillins presentation he highlighted that NGS has three development phases for OPUS underway to support the Modernized NSRS:

    OPUS-S 5.2: Multi-GNSS with similar functionality as current OPUS-S

    • Occupations – one hour or greater
    • Standard deviations estimate instead of peak-to-peak values

    OPUS 6.0: Rewrite of code base in cloud-native application

    • single/multiple occupations on a single mark
    • enhanced sharing functionality
    • Occupation Time – minimum of 4 hours
    • NGS will review and add these data to the next reference epoch coordinate (REC) adjustment

    OPUS 6.1: Extension of OPUS 6.0 for multiple marks in a network

    • Replace OPUS-Projects functionality
    • Multiple occupations on a network of marks (campaign-style surveys)
    • Will allow multiple occupations on a single mark – uploads ~10 data files on a mark
    • Built for future expansion to support other geodetic measurements (classical, leveling)

    I want to emphasize that, in my opinion, NGS is doing a fantastic job with the limited resources that they have.  That said, I still have an issue with adopting the new NSRS without having a process for users to submit data to NGS for review, approval, and publication by NGS.  This may not be an issue if NGS’s OPUS 6.1 is available soon after the new NSRS is adopted by the Federal Agencies.

    My August 2025 GPS World Newsletter discussed the OPUS products under development and, as I mentioned at that time, in my opinion, may be a problem for some users.  As I stated in my August newsletter, for the new NSRS to be successfully implemented by users, it is essential that all the necessary software tools are available to enable users to submit projects for review, approval and publication by NGS. 

    Excerpt from August 2025 GPS World Newsletter

    “The NGS News announcement provides a list of products that will be available and a list of products that will not be available when the new NSRS is adopted. Users need to understand what products will not be available after NGS officially adopts the new NSRS so they can determine what that means to their workflow process and client requirements.  In my opinion, for the new NSRS to be successfully implemented by users, it is essential that all the necessary software tools are available to enable users to submit projects for review, approval, and publication by NGS.  As many of you know, when I worked for NGS, I was the Project Manager of the North American Vertical Datum of 1988 (NAVD 88). That said, from my experience as the NAVD 88 Project Manager, having the appropriate tools available was important for users to implement NAVD 88.  As a matter of fact, NGS accepted and processed vertical control data in both NGVD 29 and NAVD 88 for a period to assist users in the implementation of the new vertical reference datum.”

    NGS does state that users will be able to submit data through OPUS and OPUS Share to obtain estimates of coordinates in the new NSRS.  Unfortunately, using OPUS-Share results that are NOT official NSRS coordinates published by NGS could lead to confusing results and potential lawsuits since NGS does not stand behind the results and recommends NOT using OPUS-Share results for geodetic control.

    “This is NGS’s statement on OPUS-Share: Additionally, the popular function of “sharing” your solution with others (colloquially called “OPUS-Share”) will be retained, but with appropriate caveats that the shared solution should not be used as geodetic control. These shared solutions will be available through the geodetic mark pages of the DDS.“

    Why should users use OPUS-Share to establish geodetic control when NGS advises against relying on OPUS-Share for establishing geodetic control?  OPUS-Share results are not officially submitted to NGS for review, approval, and publication on an NGS Datasheet. I don’t believe this approach will meet the needs of users who require their projects to be reviewed, approved, and published by NGS.

    Finally, as someone deeply invested in the geodetic community—having retired from NGS and followed NGS developments closely for years—my overall opinion on the NSRS modernization rollout plan for the remaining products is cautiously positive, but with some genuine concerns that I believe NGS and stakeholders should address head-on to ensure a smoother transition.

    The phased beta release approach (starting in 2025 and continuing through 2026) is smart and user focused. Releasing components incrementally on the beta site, allowing at least 6 months of public testing and feedback per major piece (and overall testing extending beyond the final release), shows NGS is prioritizing stability over speed. The emphasis on stakeholder input, FGCS approval (now looking like late 2026 or early 2027), and a multi-month transition to the official site align well with best practices for such a massive shift. It’s encouraging to see private industry partners (e.g., ESRI, Blue Marble) already engaging deeply and planning implementations—success will depend on industry buy-in.

    That said, here are my main thoughts and concerns I’d share directly with NGS (perhaps via [email protected], user forums, or upcoming webinars/Q&A sessions):

    Timeline uncertainty: Clearer, more frequent milestone updates (beyond the Track Our Progress page) would help manage expectations. For example, monthly or bimonthly “status dashboard” with remaining beta items and projected release windows would be invaluable.

    OPUS and processing continuity: The shift away from OPUS-Projects 5 toward OPUS 6 and OPUS-Share is logical for a modern GNSS-centric system, but the lack of a firm end-of-support date for legacy OPUS tools (beyond “at least 6 months’ notice”) creates planning headaches for firms with ongoing projects. NGS should commit to a longer grace period—or ideally a defined parallel support window—for legacy OPUS tools (particularly OPUS-Projects 5) after the official adoption of the modernized NSRS.

    Data access and usability in the new DDS: The revamped Geodetic Mark/Station Pages, updated NGS Map interface, and overall Data Delivery System sound promising (more visual, integrated RECs/SECs, photos, etc.), but surveyors rely heavily on reliable, scriptable access (e.g., for bulk queries or automation). If the new web-based system lacks robust APIs or export options comparable to current datasheets/legacy tools, it could hinder efficiency. Beta testers should push hard on this during the 6+ month window.

    Transformation tools and legacy data handling: Enhanced web-based tools are key for bridging old-to-new (NAD 83/NAVD 88 to NATRF2022/NAPGD2022), but users need confidence that transformations minimize errors, especially in deformation-prone areas.

    Communication and outreach: NGS has improved with webinars, the Presentations Library, and beta feedback channels, and more targeted outreach to state agencies, professional societies (NSPS, AAGS), and software vendors has helped. That said, many in the field still feel “in the dark” about practical impacts—case studies, training resources, and FAQs tailored to common workflows would go far.

    In summary, the plan is thoughtful and deliberate, reflecting lessons from past delays. If NGS maintains transparency, incorporates feedback aggressively during beta, and ensures vendor readiness, the modernized NSRS will be a major win for accuracy, sustainability, and GNSS alignment.

    I’d encourage anyone reading this (including NGS staff) to test the beta products actively, submit detailed feedback, and participate in forums/Q&As. The community input will make or break the success of this once-in-a-generation update.

  • A New Year’s resolution for National Spatial Reference System users

    A New Year’s resolution for National Spatial Reference System users

    Happy New Year! I’ve always felt that a fresh calendar represents a world of new opportunities, and I wish you all a fantastic 2026. For many, this is a season for reflection and self-improvement, with goals typically centered on fitness, faith, personal growth or career milestones.

    As regular readers of this newsletter know, my primary focus over the past year has been to champion the importance of geodesy and to prepare the geospatial community for the National Geodetic Survey’s modernized National Spatial Reference System (NSRS).

    To see how modern tech would handle such a specialized professional niche, I asked the AI chatbot Grok: “What would be a good New Year’s resolution for a user of the National Spatial Reference System?”

    The response was quite insightful. Take a look at what it suggested below.

    What would be a good New Year’s Resolution for a user of the National Spatial Reference System? (Grok’s Response)

    Fun and Practical New Year’s Resolutions for NSRS Users

    As we head into 2026, the modernization of the NSRS is in full swing. NOAA’s National Geodetic Survey (NGS) released the first beta products in June 2025, with ongoing rollouts and testing throughout the year. The full transition to new frames like NATRF2022 and NAPGD2022 is expected soon, bringing centimeter-level accuracy aligned with GNSS and global standards—but it requires preparation.

    Here are some timely, geodesy-inspired New Year’s resolutions tailored for surveyors, GIS professionals, engineers, and anyone relying on the NSRS:

    1. Fully transition workflows to the modernized NSRS. Commit to updating software, processes, and datasets for the new terrestrial reference frames and geopotential datum. Test tools on the NGS Beta site and provide feedback to help shape the final rollout.

    esri.com

    gpsworld.com

    1. Achieve new heights (and accuracies) in 2026. Embrace NAPGD2022 for more precise orthometric heights. Resolve to reprocess key projects with updated transformations (via NCAT or VDatum) and say goodbye to NAVD 88 quirks.
    1. Stay grounded in best practices. Incorporate the latest NGS guidelines, like NOS NGS 92 standards for GNSS surveys. Attend webinars and workshops, or review resources, to keep your positioning sharp.

    gpsworld.com

    1. Contribute to the system. Submit high-quality GNSS data via OPUS-Share or participate in crowdsourced efforts to improve the network. Help make the NSRS even more robust for everyone.
    1. Measure progress monthly. Track how the modernization impacts your work—review coordinate shifts, audit legacy data, and plan for smoother integrations in future projects.

    These resolutions blend practicality with the spirit of improvement that defines geodesy. Happy New Year—may your positions be accurate, your elevations precise, and your datums forever modernized! For the latest updates, check geodesy.noaa.gov.

    It’s no surprise that Grok highlighted the NSRS modernization; it even incorporated a photo of a geodetic benchmark I took for my July 2025 GPS World Survey Scene newsletter.

    Understanding that most AI chatbots personalize results using past interactions (unless disabled), I wanted to test this. After clearing my cache and deleting all previous Grok interactions, I posed the question again.

    You can find that second, impersonalized response below.

    Second Response from Grok

    What would be a good New Year’s Resolution for a user of the National Spatial Reference System? Grok’s Second answer.

    Here are some practical, realistic, and useful New Year’s resolutions tailored for someone who regularly works with the NSRS whether you’re a surveyor, GIS professional, geodesist, engineer or data manager:

    1. “This year, I will stop mixing epochs without documenting them.” Resolve to always record the reference epoch (e.g., 2010.0, 2020.00) when I use NAD83(2011), NAD83(CORS96), NAD83(2011) epoch-specific coordinates, or when I transform to ITRF2020/2020.0. Bonus: add epoch to layer names and metadata.
    2. “I will run OPUS or CSRS-PPP at least once a month to keep my local control fresh.” Make it a habit to periodically re-observe a trusted point and submit it to NOAA’s OPUS (or CSRS-PPP in Canada) to verify that my local network hasn’t drifted too far from the national datum.
    3. “I will finally transition at least one active project to the modern NSRS (NAD83(2011)/NAVD88 → NATRF2022 / NAPGD2022).” Pick one ongoing or new project and do the full datum shift. Learn the tools (NADCON5, VERTCON3, GEOID18 → GEOID2022) and document what changed.
    4. “I will replace every ‘NAD83’ label that doesn’t specify an epoch or realization with something more precise.” No more generic “NAD83” in reports, plats, or metadata. Aim for “NAD83(2011) epoch 2010.0” or “NAD83(2011) CORS-derived” — or better yet, start using NATRF2022 when appropriate.
    5. “I will learn to use the NGS Coordinate Conversion and Transformation Tool (NCAT) fluently.” Commit to doing at least 5 conversions or transformations per month in NCAT instead of relying on old software or hand-calculated factors.
    6. “I will check the NGS Data Explorer / Datasheet for every benchmark or CORS I plan to use — before I use it.” No more assuming a published value is still good. Make it a 2-minute ritual to look up the latest adjusted position and velocity.
    7. “I will attend at least one NGS webinar or read one Bluebook chapter in 2026.” The NGS webinar series is free and excellent. Pick one session (e.g., on GEOID2022, NATRF2022 implementation, or GNSS vector processing) and actually watch it.
    8. “I will prepare a small ‘before/after’ datum comparison report for my organization or clients.” Quantify what the 2022–2025 NSRS modernization means in your typical project area (horizontal shift, orthometric height change). Even a one-page summary builds understanding and credibility.
    9. “I will stop treating GEOID18 as the final word and start using GEOID2022 for new work.” Especially important for projects that will live past 2025, as NGS is phasing out support for older geoids.

    Pick one or two that feel achievable and most relevant to your day-to-day work. My personal favorite starter resolution for most NSRS users in 2026: “In 2026, I will clearly label the datum, realization, epoch, and geoid model on every deliverable I produce.”

    That one habit alone dramatically reduces confusion downstream.

    I really appreciate Grok’s responses because they address crucial issues that many geospatial users either overlook or take for granted, emphasizing the importance of proper documentation and associated metadata.

    Key Resolution Examples:

    • Specificity: “I will replace every ‘NAD83’ label that doesn’t specify an epoch or realization with something more precise.”
    • Verification: “I will check the NGS Data Explorer / Datasheet for every benchmark or CORS I plan to use — before I use it.”

    It is important to note that the AI chatbot assumes the modernized NSRS has already been adopted, which, as of January 2026, is not the case. This highlights that AI still has limitations and requires human oversight.

    I challenge you to ask your own AI chatbot a similar, niche question related to your profession and compare its responses.

    Beyond the specific technical corrections, Grok provided excellent general advice for any geospatial professional. Take, for example, action items 1 and 5 from its first response:

    • Transition Workflows: Commit to fully updating software, processes, and datasets to align with the new terrestrial reference frames and geopotential datum.
    • Measure Progress Monthly: Track the real-world impact of modernization by reviewing coordinate shifts, auditing legacy data, and planning for smoother integrations in upcoming projects.

    Even though the modernized NSRS has not yet been officially adopted as of January 2026—with official release and FGCS approval expected later this year—following these steps now ensures you are prepared for the official transition when it occurs.

    So, how do we put this advice into action? In my October 2025 GPS World Survey Scene newsletter, I highlighted the work of Dana J. Caccamise II, NGS regional geodetic advisor. Dana has developed vital guidance materials shared with federal agencies—such as the Federal Geographic Data Committee (FGDC) and professional organizations including National Society of Surveyors (NSPS), American Society of Photogrammetry and Remote Sensing (ASPRS), and American Association for Geodetic Surveying (AAGS). 

    To help your team prepare for the official transition later this year, I’ve included a box titled “Questions to Guide a Self-Assessment of Your Operation and Products.” These questions, originally featured in my October newsletter, are designed to ensure your organization is fully equipped to implement the new NSRS the moment it is adopted.

    Questions to Guide a Self-Assessment of Your Operation and Products

    1. Are you generating or using geospatial data (or doing both)?
      • If so, your workflows are likely dependent on geodetic control tied to one or more NGS products. The upcoming NSRS update will affect these dependencies. (See the box titled “List of NGS Products and Services.”)
    2. Do you know if your mission, project, or datasets depend on NGS products?
      • Identifying whether and how your entity relies on NGS products is a critical first step in assessing potential impacts.
    3. What are your accuracy, precision, and shelf-life requirements for geospatial data?
      • Understanding your mission’s specific data requirements ensures you can evaluate whether NSRS modernization will meet your operational needs without unnecessary adjustments.  This should include plans to accommodate greater accuracy in the future.
    4. Do you know how your entity accesses and utilizes geospatial data?
      • Are you obtaining it directly from NGS or indirectly through third-party vendors (e.g., RTN systems, GIS platforms, GNSS companies)?
      • Many entities rely on geodetic control without realizing it. NGS’s foundational data and frameworks are often invisible and seamlessly embedded within the tools and services offered by third-party vendors, such as GIS platforms, survey equipment, and software providers. These vendors, in turn, depend heavily on NGS products like the NSRS to ensure their tools are accurate and functional. Understanding this indirect reliance is crucial for preparing your workflows and ensuring continuity as the NSRS is modernized.
    5. Where does your entity fit in with the geodetic workflow?
      • Does your entity create integral products (e.g., GNSS data, Lidar data) on which other products depend?
      • Evaluating these dependencies will help you determine the scope of NSRS modernization impacts.
    6. What are your project requirements for data accuracy and longevity?
      • Assess whether your data accuracy thresholds and long-term usability align with the modernized NSRS.
    7. Have you evaluated workflows and identified potential impacts in areas affected by significant ground movement (e.g., regions with tectonic shifts, vertical land motion, and, most notably, subsidence) 
      • Identifying potential risk or disruption areas can guide prioritization and help mitigate impacts on critical operations.

    In my October 2025 GPS World newsletter, I mentioned that the National Geodetic Survey (NGS) would be hosting a meeting with Federal geospatial agencies under the auspices of the Federal Geodetic Control Subcommittee (FGCS). The purpose is to increase awareness and coordinate the NSRS Modernization across the government.

    While the original meeting scheduled for October 15, 2025, was canceled due to the Federal Government Shutdown, it has been officially rescheduled for Wednesday, January 21, 2026. This meeting will be critical for aligning agency engagement strategies and self-assessments ahead of the final adoption of the new datums.

    As stated in my October 2025 newsletter, the primary objectives of this meeting are to:

    • Increase awareness of the National Spatial Reference System (NSRS) Modernization rollout schedule and engagement strategy, including self-assessment and interaction between official departmental working groups and an NGS point of contact.
    • Within other Departments, connect decision-makers to those who accomplish NSRS modernization tasks and designate points of contact to interface with NGS capacity-building efforts.
    • Share experiences and strategies among federal agencies concerning NSRS Modernization self-assessment and preparation.
    • (New) Formally transition the foundational beta products (released in May 2025) from preliminary to final.
    • Gather questions, discuss anticipated challenges, and identify opportunities to support each other through this transition.

    The FGCS plays a central role in coordinating geodetic activities across the federal government, including the development of standards and the promotion of the use of authoritative geodetic control (e.g., CORS, geoids) to ensure that geospatial data is accurate, accessible, and interoperable, and to advance the modernization of NSRS across agencies and recommend the adoption of the modernized NSRS by FGDC as the official basis for geodetic control in the United States. It is my understanding that this meeting is open to the public (virtually) for listening and observation.  The box titled “Federal Geodetic Control Subcommittee Meeting” provides the agenda of the January 21, 2026, meeting.

    Federal Geodetic Control Subcommittee Meeting Agenda held January 21, 2026.
    Federal Geodetic Control Subcommittee Meeting Agenda held January 21, 2026.

    To join the meeting virtually, registration is required. You can find all the necessary details and a direct link to sign up in the box titled “Registration for the Virtual Attendance of the Meeting.”

    Registration for the Virtual Attendance of the Meeting

    NOAA’s National Geodetic Survey (NGS) invites you to the upcoming Federal Geographic Data Committee (FGDC) Federal Geodetic Control Subcommittee (FGCS) meeting.

    • Date: Wednesday, January 21, 2026
    • Time: 1:00 PM – 4:00 PM ET
    • Location: Hybrid meeting, offering both in-person attendance at NOAA Offices in Silver Spring, MD, and virtual participation via WebEx.
      • If you plan to attend in person, please email [email protected] so we can ensure building access.

    If you plan to attend virtually, here is the registration link: https://ngs-nos-noaa.webex.com/weblink/register/r53ab4d202de3bb20df12d9364862ff0f

    As I mentioned in my October 2025 GPS World Survey Scene newsletter, several organizations have formed working groups to address the new NSRS. The National Society of Surveyors (NSPS) has released a story map to inform the professional surveying community and is developing guidance and case studies. The American Association for Geodetic Surveying (AAGS) is collaborating with NSPS. The American Society of Photogrammetry and Remote Sensing (ASPRS) has prepared materials available on its website.

    In October 2025, NSPS held its Fall meeting.  The box titled “Excerpts from 2025 NSPS Fall Meeting Report: October 17, 2025” contains excerpts from the report provided by Richard Kleinmann, Wisconsin NSPS Director, on the working group’s activities being performed by the National Society of Professional Surveyors (NSPS) Professional Standards NSRS Modernization Subcommittee.

    Excerpts from 2025 NSPS Fall Meeting Report: October 17, 2025

    Submitted by: Richard Kleinmann PLS, Wisconsin NSPS Director

    Subcommittee Purpose: To promote awareness, adoption, and readiness for the implementation of the Modernized National Spatial Reference System (NSRS) in cooperation with the National Geodetic Survey (NGS) and other geospatial groups.

    Activities: NSPS leadership and the NSRS Modernization Subcommittee continue to work closely with NGS to promote awareness, adoption, and readiness for the new 2022 datums, which are expected to be approved sometime in 2026. Due to federal funding challenges occurring in 2025, NSPS felt it necessary to intensify its support of NGS and the modernization of the NSRS which was the genesis of this subcommittee.

    As an outgrowth of interactions between NSPS & NGS during NGS quarterly meetings and at geospatial events such as the ESRI User Conference and Geo Week, the NSPS leadership team, and subsequently the NSRS Modernization Subcommittee, began developing a suite of resources — including an ArcGIS StoryMap with several resources useful for the transition.   See the link for the NSPS ArcGIS Story map here: https://share.google/oOAIapPQnux5q8nwl

    The NSRS Modernization Subcommittee is also working on a series of documents originally developed by Dana J. Caccamise of NGS intended to be used by Federal Agencies in the transition to the new datums.  We are adapting the documents to change the “voice” from NGS to NSPS and the intended audience to state, regional, county and local agencies, as well as private practitioners, to help them transition smoothly to the modernized NSRS.  At this point, the document package includes:

    • Initial outreach tools (Email & Leadership Memo), 
    • Technical readiness resources (Self-Assessment Checklist & Survey)
    • Briefing materials for agency coordination (Presentation Template)

    These document resources are being developed with the hope to share them via NSPS social media outreach efforts and possibly a geospatial information “hub” shared by NSPS and other geospatial organizations.

    Proposed Whitepapers/Use Case Reports: The intent of these whitepapers is to is to provide a somewhat higher-level view of how the transition to the new datums/frames can be accomplished by showing what tools are available and what to consider when designing a project approach.  Our hope is to promote the adoption of the new datums and share the benefits of doing so.  Basically, adopting a “be prepared, not scared” attitude.  We are looking for people willing to share their solutions so others can benefit from their experience and be more likely to be early adopters.  It is not our intent to develop detailed step by step recipes that can be blindly followed because every geographic region has their unique circumstances that need to be considered but the white papers will instead supply the foundation for them to confidently build a project approach that works in their situation.

    Coordination with other working groups: NSPS is looking forward to coordinating with similar Working Groups that NGS has encouraged to be formed by the American Society for Photogrammetry and Remote Sensing (ASPRS) and the American Association for Geodetic Surveying (AAGS). There are several Task Forces and Committees formed on the state level that are also working on adoption and implementation issues specific to their states.  Together, these efforts aim to build understanding, reduce uncertainty, and support the geospatial community’s successful implementation of the updated reference framework.   NSPS and NGS have committed to having a significant presence at Geo Week in Denver, Colorado, on February 16-18, 2026. 

    As mentioned in the working group’s report, “As an outgrowth of interaction between NSPS & NGS during NGS quarterly meetings and at geospatial events such as the ESRI User Conference and Geo Week, the NSPS leadership team and subsequently the NSRS Modernization Subcommittee began developing a suite of resources — including an ArcGIS StoryMap with several resources useful for the transition.   See the link for the NSPS ArcGIS Story map here: https://share.google/oOAIapPQnux5q8nwl.

    The box titled “NSPS ArcGIS Story Map” offers a detailed look at this resource, which visually illustrates the impact and benefits of the upcoming NSRS modernization.

    NSPS ArcGIS Story Map
    NSPS ArcGIS Story Map

    The website has five buttons:

    • Overview
    • What to Expect
    • How to Prepare
    • Resources
    • Note to Users

    The section titled “The Overview Section” details the essential information — who, what, where, when, and why — regarding the new, modernized NSRS.  Additional information is available on the website.

    Overview

    WHO: The  National Geodetic Survey  (NGS), located within the National Oceanic and Atmospheric Administration (NOAA) of the United States government.  The NGS is responsible for defining, maintaining, and providing access to the country’s positioning infrastructure called the  National Spatial Reference System  (NSRS).

    WHAT: Is updating the NSRS  – horizontal (geometric, NAD 83) and vertical (geopotential, NAVD 88 and local island vertical datums PRVD02, USVI09, ASVD02, GUVD04, HAWAII – Local Tidal) geodetic datums, an effort that has been underway since 2007.

    WHERE: The North American, Pacific, Caribbean, and Marianas plates.

    WHEN: Now – rollout is underway. An updated  Federal Register Notice was released on October 9, 2024.   Alpha and  Beta products are being released, with full replacement of the NSRS anticipated in 2026.

    WHY: These datums have been in use since GPS was in its infancy – i.e., for decades, and there are known limitations that the new system addresses:

    • NAD 83 is not as geocentrically defined as today’s positioning technologies demand, meaning not referenced to the center of Earth’s mass, by about 2.24 meters based on the latest international estimates. This is problematic when using Global Navigation Satellite Systems (GNSS), which orbit about and provide positions relative to the center of the Earth.
    • NAD 83 grouped the North American and Caribbean plates in its definition.  The updated system has broken those two plates out (because we now understand how to measure how the plates rotate individually) in addition to the Pacific and Marianas plates included in NAD 83, resulting in definitions for four Terrestrial Reference Frames (TRFs): NATRF2022, PATRF2022, MATRF2022, and CATRF2022.
    • Continental drift and vertical land movement were not accounted for in the existing NSRS.  Reference epochs (timestamps, for instance) for coordinates have been introduced for survey data to help us better understand movement or change over time.
    • Based on current international geoid estimates, NAVD 88 is biased by approximately 1.5 meters and tilted by 1 meter coast-to-coast.
    • There are currently multiple vertical datums.  The new system will consist of one.
    • NAD 83 and NAVD 88 were designed independently, resulting in reduced accuracy.  In the new system, they were designed together, resulting in better integration and higher accuracy.
    • GEOID 18 and previous models were hybrid models “warped” to match leveled benchmarks. GEOID2022 will be a more consistent and stable model as it is a purely gravimetric geoid model.
    • Currently, both physical marks and continuously operating GNSS stations are relied upon for the existing NSRS. Physical marks degrade and are destroyed over time, negatively affecting height and position data. The modernized NSRS will rely exclusively on GNSS stations.
    • State Plane Coordinate System 83 (SPCS 83) includes high levels of distortion for many areas. The modernized SPCS2022 minimizes distortion or scale error (the difference between ground and grid measurements) at the topographic surface rather than the reference ellipsoid surface, and is designed to minimize distortion in populated or high-use areas.
    • An important change between SPCS 83 and the upcoming SPCS2022 is that only the international foot (1 foot = 0.3048 meter, exactly) will be supported, which differs from SPCS 83, with some states officially using the international foot while others use the U.S. survey foot (1 foot = 1200/3937 meters). This is consistent with the  deprecation of the U.S. survey foot initiated by the National Institute of Standards and Technology (NIST) at the end of December 2022.

    The website makes it easy to spread the word about NSRS modernization. By clicking the share button on the right side of the page, you can access several ways to distribute the story map with colleagues or on social media.

    The Sharing the NSPS ArcGIS Story Map includes more details — it even includes an embedded QR code that you can scan to open the map directly on your mobile device.

    You can access it on your mobile device using the code below.

    NSPS ArcGIS Story Map QR Code
    NSPS ArcGIS Story Map QR Code

    For those who prefer a physical copy or a clean PDF, the site also offers a print-friendly version. See the box titled “NSPS ArcGIS Story Map – Print View” for instructions on how to access it. This 15-page document provides all the same information as the interactive site in a consolidated, easy-to-read format.

    NSPS ArcGIS Story Map – Print View
    NSPS ArcGIS Story Map – Print View

    As highlighted in the NSPS working group’s October report, both NSPS and NGS are committed to a major presence at Geo Week in Denver, Colorado, from February 16–18, 2026.

    A key session, “NSRS Modernization – The Latest Technical Updates,” is currently scheduled for February 17, 2026, at 2:00 PM. For more details on the presentation and speakers, refer to NSRS Modernization – The Latest Technical Updates below.

    2:00 PM – 3:30 PM MT

    Bluebird Ballroom 1A

    The National Spatial Reference System (NSRS) is undergoing a major transformation to provide more accurate, accessible, and consistent geospatial reference data across the United States. This session will present the latest technical updates on NSRS modernization, including advancements in geodetic reference frames, updated survey standards, and enhanced tools for positioning and measurement. Attendees will learn how these changes impact surveying, mapping, infrastructure, and engineering projects, and gain practical guidance for integrating modernized NSRS data into workflows. This session is essential for professionals seeking to stay current with the evolving national geospatial reference framework.https://mail.google.com/mail/u/0/#search/lfoster%40esri.com/FMfcgzQcqtcPbfppZtnTpZZWDMkQcXfk?projector=1&messagePartId=0.1

    I wish you all a prosperous 2026 filled with wonderful new relationships, exciting opportunities, and continued happiness and success.

    Happy New Year!

  • Scripps Institution of Oceanography expands geodetic program

    Scripps Institution of Oceanography expands geodetic program

    My September GPS World newsletter highlighted the new California Spatial Reference Network, labeled CSRN Epoch 2025.00. These coordinate changes will impact geospatial users across California, and understanding the transition process is important for preparing for the modernized National Spatial Reference System (NSRS), expected to be adopted in 2026.

    This newsletter will focus on the California Spatial Reference Center (CSRC) and the Geodetic Program at Scripps Institution of Oceanography (SIO).

    CSRC, founded in 1997 and formally dedicated in 2001, develops and maintains a modern network of GPS control stations to provide a reliable spatial reference system for California. Created as a partnership of surveyors, engineers, GIS professionals, the National Geodetic Survey (NGS), Caltrans, and the geodetic and geophysical communities, the CSRC’s mission is to produce a self-sustaining, up-to-date geodetic control network for the state.

    The CSRC holds Coordinating Council meetings to review CSRC activities and related state surveying and mapping efforts. The box titled “CSRC Coordinating Council 2025 Fall Meeting” lists the agenda for the most recent meeting. I attend these meetings virtually; they are consistently informative and I enjoy participating.

    Image: CSRS website
    Image: CSRS website

    Dr. Yehuda Bock’s Director’s Report (SOPAC/CSRC Director, Dept. IGPP, Scripps Oceanography, UCSD) is available for download from the CSRC website: http://sopac-csrc.ucsd.edu/index.php/csrc-presentations/ (note: large file). At the Fall Coordinating Council Meeting Yehuda opened with a presentation on the new California Spatial Reference Network, CSRN Epoch 2025.00. I encourage readers to download the presentation or read my September GPS World newsletter, which highlighted CSRN Epoch 2025.00. This newsletter will focus on the Geodetic Program at Scripps Institution of Oceanography (SIO).

    Image: CSRC website
    Image: CSRC website

    In my November 2023 GPS World newsletter, I noted NGS’s announcement of the NOAA FY23 Geospatial Modeling Competition awardees. In my March 2024 GPS World newsletter, I  highlighted Scripps Institution of Oceanography’s (SIO) proposal. As noted there, Yehuda’s proposal included three activities:

    • Create a formal Geodesy Program at SIO to address the nationwide deficiency of geodesists. Expand current geophysics curriculum – funding for five graduate students.
    • Develop an IFDM to supplement the NSRS for users in regions with significant ground motions, using GNSS and InSAR/GNSS displacement fields (funded by NASA projects) and underlying geophysical models. CSRC will exercise the IFDM through its community of public, private and academic users of precise spatial referencing in our challenging region of secular and transient crustal movements.
    • Investigate a unified vertical reference frame, including a marine geoid optimized to be consistent with the full spectrum of observations from modern gravimetric geoids (e.g., GRAV-D, ICGEM), remotely sensed observations (e.g., SWOT, ICESat-2), in situ ocean observations and assimilating ocean models and the TRF.

    At the Fall Coordinating Council Meeting, Yehuda provided an update on the status of the Geodesy Program at SIO.  It was mentioned that some of the students are funded by the National Geodetic Survey (NGS)’s grant but others are funded by the National Geospatial-Intelligence Agency (NGA), United States Geological Survey (USGS), and the Office of Naval Research (ONR).

    Image: CSRC website
    Image: CSRC website
    Image: CSRC website
    Geodesy track curriculum. (Image: CSRC website)
    Geodesy track curriculum. (Image: CSRC website)

    As mentioned in the Director’s report, they have initiated bi-weekly geodesy track seminars to discuss research projects related to NGS and other grants.  Four videos by students discussing their projects were shown during Yehuda’s presentation. 

    The following are the titles and presenters of the four research projects:

    • San Jacinto Fault Zone by Neil Waldhausen
    • Probing Antarctic basal ice state using airborne geodesy by Briar Conger
    • Repeat Pass Interferometry by Rubi Garcia Gonzalez
    • Hydrologic monitoring with GRACE/GRACE-FO by Logan Platt

    San Jacinto Fault Zone by Neil Waldhausen

    I have included a few bullets summarizing their project and a few captured images from the videos.  I would encourage everyone to download the presentation to listen to the short videos by these students. The presentations are only 90 seconds but are very interesting. Readers can contact the speakers through the University to find out more about their research.

    Summary of the “San Jacinto Fault Zone” video:

    • Neil uses GNSS to measure velocities and strain rates around the San Jacinto Fault.
    • He focused on the Anza gap, a 20-km segment of the fault.
    • He re-surveyed about 50 monuments that had been occupied over past decades.
    • His work has lowered uncertainties in many site velocity measurements.
    • His aim is to further reduce uncertainties in strain-rate and slip-rate estimates to better understand the Anza gap’s mechanics.
    San Jacinto Fault Zone by Neil Waldhausen.
    San Jacinto Fault Zone by Neil Waldhausen.
    San Jacinto Fault Zone by Neil Waldhausen.
    San Jacinto Fault Zone by Neil Waldhausen.
    Image: CSRC Website
    Image: CSRC website

    Summary of the “Probing Antarctic Basal Ice State Using Airborne Geodesy” video:

    • Briar’s project uses gravity and radar data to study basal hydrology — water flow beneath glaciers and ice sheets, including subglacial lakes, channels, and pressure-driven water movement.
    • He conducted fieldwork on the East Antarctic Ice Sheet during the 2023–24 season.
    • He collected airborne gravity and GNSS data from a converted DC-3 aircraft.
    • Data processing uses both PPP and differential positioning methods.
    • His aim is to improve long-term sea-level rise predictions.
    • He is also developing a fixed-wing UAV capable of collecting lidar, gravity, and photogrammetry data.

    Probing Antarctic Basal Ice State Using Airborne Geodesy by Briar Conger

    Probing Antarctic Basal Ice State Using Airborne Geodesy by Briar Conger.
    Probing Antarctic Basal Ice State Using Airborne Geodesy by Briar Conger.
    Image: CSRC website
    Image: CSRC website

    Summary of the “Repeat Pass Interferometry” video:

    • Rubi used repeat-pass interferometry (phase gradient) to map small-scale surface deformation.
    • The phase gradient is the change in interferometric phase between neighboring pixels; unlike the ambiguous single-pixel phase (wrapped within 2π), the gradient gives a continuous local rate of change useful for analysis.
    • She compared fractures identified by phase-gradient analyses with historic fracture databases.
    • Her ongoing work includes applying Andersonian faulting theory to assess whether fractures formed before or after earthquakes.
      • Andersonian faulting (Anderson’s theory of faulting) is a geological framework for interpreting crustal stress and fault geometry; it’s used to interpret InSAR-measured deformation. While not a method of analysis for InSAR data itself, it serves as a critical interpretive tool for understanding the ground deformation patterns measured by InSAR.

    Repeat Pass Interferometry by Rubi Garcia Gonzalez

    Repeat Pass Interferometry by Rubi Garcia Gonzalez.
    Repeat Pass Interferometry by Rubi Garcia Gonzalez.
    Image: CSRC website
    Image: CSRC website

    Summary of the “Hydrologic monitoring with GRACE/GRACE-FO” video:

    • Logan described using satellite measurements of tiny changes in Earth’s gravity to track mass movement and better understand groundwater and the water cycle.
    • He relied on GRACE and GRACE-FO data.
      • The Gravity Recovery and Climate Experiment (GRACE) and its successor mission, GRACE-Follow On (GRACE-FO), are Earth-observation missions that use twin satellites to precisely map changes in Earth’s gravity field over time. This unique method allows scientists to track the movement of mass, primarily water, around the planet
    • He used the GRACE data to look at changes in California’s Water storage from 2004 to 2024.
      • Results indicate a decline due to drought and heavy ground water usage, with more water being stored in northern California than southern California.
    • This research supports water management, climate-change impact assessment, and strategies for sustainable groundwater use.

    Hydrologic Monitoring with GRACE/GRACE-FO by Logan Platt

    Hydrologic Monitoring with GRACE/GRACE-FO by Logan Platt.
    Hydrologic Monitoring with GRACE/GRACE-FO by Logan Platt.
    Hydrologic Monitoring with GRACE/GRACE-FO by Logan Platt.
    Hydrologic Monitoring with GRACE/GRACE-FO by Logan Platt.
    Image: CSRC Website
    Image: CSRC website

    A new InSAR textbook, authored by several internationally recognized researchers, was also announced. Funded by the National Geodetic Survey and published Open Access, the book is available for free download. It’s a large file, but anyone working with InSAR data should obtain a copy.

    New InSAR Textbook

    Image: CSRC website
    Image: CSRC website

    Table of Contents of New InSAR Textbook

    If you’ve read my newsletters, you know I’m passionate about advancing geodesy. I wanted to share one of Yehuda’s slides, “What Geodesy Can Tell Us About Earth,” because the four students are working on projects tied to real-world problems. The slide highlights geodesy’s importance and the many professions that rely on its findings.

    What geodesy can tell us about Earth. (Image: CSRC website)
    What geodesy can tell us about Earth. (Image: CSRC website)
  • Are you ready for NSRS modernization? What the upcoming changes mean for your geospatial data

    Are you ready for NSRS modernization? What the upcoming changes mean for your geospatial data

    In my August 2025 GPS World newsletter column, I highlighted that a colleague reminded me that the National Geodetic Survey’s (NGS) new National Spatial Reference System (NSRS) is more than a technical upgrade. It offers a prime opportunity to review and improve current processes and workflows, examine existing products and considerations, and plan strategically for future needs. By auditing geospatial data dependencies now, NSRS users can assess how transitioning to the new datum will affect workflows, datasets and operational decision-making.

    Several organizations have formed working groups to address the new NSRS. The National Society of Surveyors (NSPS) has released a story map to inform the professional surveying community and is developing guidance and case studies. The American Association for Geodetic Surveyor (AAGS) is collaborating with NSPS. The American Society of Photogrammetry and Remote Sensing (ASPRS) has prepared materials available on its website. Additionally, under the leadership of Gary Thompson, the North Carolina Geodetic Survey established the North Carolina 2022 Reference Frame Working Group. The group’s goal is to address issues related to the implementation of the datum change in 2026. It includes representatives from North Carolina agencies involved in producing or using geospatial products and services.

    Agencies Involved in the NC 2022 Reference Frame Working Group
    NC Geodetic SurveyNC DOT HydraulicsNC State Mapping Advisory Committee
    NC Geographic Information Coordinating Council (GICC)NC State, Land Records ManagementNC Geodetic Survey Advisory Committee
    NC Center for Geographic Information & AnalysisNC GICC Local Government CommitteeNC Society of Surveyors
    NC DOT State Location & SurveysNC State Mapping Advisory CommitteeDuke Energy
    NC DOT Photogrammetry UnitNC GICC Local Government CommitteeU.S. National Geodetic Survey

    The organizations participating in the NC RFWG are assessing how changes in the new NSRS may impact their geospatial workflows and evaluating their reliance on NGS products and services. Proactive self-assessment is essential because NGS cannot customize support for each entity’s unique needs and processes. By identifying potential challenges and opportunities early, organizations can adapt smoothly and maintain operational efficiency during the transition. The following were the key action items from the last NC RFWG meeting:

    • Create an information sheet to help local governments prepare for the data change
    • encourage agencies to consult their software vendors on support measures for the new datums
    • establish a rule for when to use the U.S. Survey Foot versus the International Foot
    • review current data files to ensure their metadata includes datum and unit information.

    Many participants of the North Carolina working group expressed interest in understanding how much the coordinates will shift with the new NSRS. While NGS’s website offers diagrams that provide a high-level overview of coordinate and product changes, many users sought more detailed information specific to North Carolina. To address this, I used NGS’s Multi-Year CORS Solution 3 (MYCS3) update of the NOAA CORS Network to ITRF2020, epoch 2020.0, to estimate the changes between the current NSRS — NAD 83 2011 (epoch 2010.0) — and the upcoming NSRS in North Carolina, such as NATRF2022 at epoch 2020.0. This approach offers a more detailed view of the magnitude of shifts in local regions. The figure titled “Approximate Differences Between NATRF2022 (Epoch 2020.0) and NAD 83 2011 (Epoch 2010.0) in NC” illustrates the approximate horizontal coordinate differences between the current NSRS and the future NSRS based on NCN CORS data. (Note that these units are in feet.) For additional information on MYCS3 and regional changes across the United States, refer to my August 2025 GPS World column.

    Approximate differences between NATRF2022 (Epoch 2020.0) and NAD 83 2011 (Epoch 2010.0) in North Carolina. Horizontal change in feet. (Credit: Dave Zilkoski)
    Approximate differences between NATRF2022 (Epoch 2020.0) and NAD 83 2011 (Epoch 2010.0) in North Carolina. Horizontal change in feet. (Credit: Dave Zilkoski)

    Differences in orthometric heights between the new NAPGD2022 and the current NAVD 88 are significant for anyone working with FEMA flood maps or preparing flood insurance elevation certificates. I used ITRF2020, epoch 2020.0, ellipsoid heights from NOAA CORS stations along with Geoid2022 values to estimate the NAPGD2022 orthometric heights at the CORS sites. As depicted in the plot, the height differences between NAPGD2022 and NAVD 88 across North Carolina range from about 0.5 feet in the southeastern region to over a foot in the northern and western regions. (Note that the units are in feet.)

    Approximate differences between NAPGD2022 and NAVD 88 in North Carolina. Orthometric height change in feet. (Credit: Dave Zilkoski)
    Approximate differences between NAPGD2022 and NAVD 88 in North Carolina. Orthometric height change in feet. (Credit: Dave Zilkoski)

    This type of information should be shared with managers of real-time GNSS networks(RTN). RTN operators could then establish a parallel beta system to enable users to understand how the new NSRS may affect their products and services. (Note: The North Carolina Geodetic Survey, which manages the NC CORS/RTN system, is considering running a pilot parallel RTN based on the new NSRS.) This data can be valuable for RTN users to assess how coordinate changes might influence their workflows. For example, it can help determine how the shifts in coordinates will affect agricultural activities such as planting, fertilizing and harvesting. Will farmers need to remap their fields, or will a transformation be sufficient?

    Fostering collaboration with stakeholders and constituents will help users better understand how the NSRS modernization impacts their products and services. Developing strategies to align geospatial data management with regulatory requirements and operational objectives will also facilitate a smoother implementation process. NGS is partnering with federal agencies and professional societies to create a self-assessment guide that helps organizations evaluate how the NSRS update affects their geospatial missions. As previously mentioned, the North Carolina 2022 Reference Frame Working Group is working with state and local agencies, as well as surveyors, to proactively address key questions and challenges. This collaboration aims to improve communication with NGS and determine whether their products and services need to be reprocessed, re-surveyed or transformed to suit the new standards.

    Each organization has its own unique geospatial requirements and a thorough understanding of its mission and needs. This is an ideal opportunity to develop a centralized plan for evaluating and managing geospatial workflows during the transition to the modernized NSRS. Challenges include aligning legacy datasets with new reference standards while ensuring data integrity. Organizations should assess the accuracy of their data in relation to the NSRS and document any necessary updates in metadata. By creating a well-structured plan that balances operational constraints, legal compliance and practical considerations, organizations can prioritize accuracy, efficiency and alignment with the updated NSRS.

    To assist others in preparing for the new NSRS, Dana J. Caccamise II, NGS regional geodetic advisor, has developed guidance materials that have been shared with federal agencies — including the FGDC and their team leaders — and professional organizations such as NSPS, ASPRS and AAGS. See the boxes titled “Questions to Guide a Self-Assessment of Your Operation and Products” and “List of NGS Products and Services — Are your workflows dependent on one or more NGS products.” The goal is to help these agencies become ready to implement the new NSRS once it is officially adopted by NGS.

    Questions to Guide a Self-Assessment of Your Operation and Products
    Are you generating or using geospatial data (or doing both)?
    – If so, your workflows are likely dependent on geodetic control tied to one or more NGS products. The upcoming NSRS update will affect these dependencies. (See “List of NGS Products and Services.”)
    Do you know if your mission, project, or datasets depend on NGS products?
    – Identifying whether and how your entity relies on NGS products is a critical first step in assessing potential impacts.
    What are your accuracy, precision, and shelf-life requirements for geospatial data?
    – Understanding your mission’s specific data requirements ensures you can evaluate whether NSRS modernization will meet your operational needs without unnecessary adjustments. This should include plans to accommodate greater accuracy in the future.
    Do you know how your entity accesses and utilizes geospatial data?
    – Are you obtaining it directly from NGS or indirectly through third-party vendors (e.g., RTN systems, GIS platforms, GNSS companies)?
    – Have you considered how updates to NGS products may impact the tools or services you rely on from these vendors?
    – Many entities rely on geodetic control without realizing it. NGS’s foundational data and frameworks are often invisible and seamlessly embedded within the tools and services offered by third-party vendors, such as GIS platforms, survey equipment, and software providers. These vendors, in turn, depend heavily on NGS products like the NSRS to ensure their tools are accurate and functional. Understanding this indirect reliance is crucial for preparing your workflows and ensuring continuity as the NSRS is modernized.
    Where does your entity fit in with the geodetic workflow?
    – Does your entity create integral products (e.g., GNSS data, lidar data) on which other products depend?
    – Does it produce derivative products (e.g., DTM, Topographic Map, Flood Insurance Rate Map (FIRM) and Flood Insurance Study (FIS) Report)?
    – Evaluating these dependencies will help you determine the scope of NSRS modernization impacts.
    What are your project requirements for data accuracy and longevity?
    – Assess whether your data accuracy thresholds and long-term usability align with the modernized NSRS.
    Have you evaluated workflows and identified potential impacts in areas affected by significant ground movement (e.g., regions with tectonic shifts, vertical land motion, and, most notably, subsidence)
    – Identifying potential risk or disruption areas can guide prioritization and help mitigate impacts on critical operations.

    List of NGS Products and Services

    Are your workflows dependent on one or more NGS products

    Products and ServicesExamples
    Geodetic Control Data– Datasheets
    – State Plane CoordinatesSurvey
    – MarksSurvey Data
    National Spatial Reference System (NSRS) Datasets– Horizontal (Geometric) reference frames
    – Vertical (Orthometric / Physical) datums
    – Geoid Models
    NSRS Tools and ResourcesNGS Geodetic Tool Kit
    – NGS PC Software such as ADJUST
    – User-Contributed Software
    – VDatum to convert elevation data
    – Other NSRS Resources such as transformation tools
    GNSS Data and SolutionsOPUS (Online Positioning User Service)
    – CORS (Continuously Operating Reference Stations)
    – Satellite Orbits
    Gravity Data– Gravity for the Redefinition of the American Vertical Datum (GRAV-D)
    – Deflection of the Vertical (DoV)
    Coastal Mapping Products– Topobathy lidar Data
    – Shoreline Mapping Products
    Aerial Imagery and Remote Sensing– NOAA Remote Sensing Division Products such as Emergency response imagery (e.g., hurricane damage)
    Analytical tools– Least squares analysis tool
    – Antenna Calibrations
    GIS and Visualization Tools– Geospatial Data such as Shapefiles and KML files for GIS applications
    – Web Services
    Educational and Reference Materials– Documentation such as NGS technical reports
    – Presentations and Posters
    – User support such as NGS Information Center and Regional Geodetic advisors
    Historical Data Archives– Legacy Products such as Older geodetic survey records and Superseded geoid models and transformation tools
    Standards and Procedures, best practices, data formats– Standards and Procedures such as NOAA Technical Memorandum NOS NGS 92
    – Data Formats such as GVX (Real-time or post-processed GNSS vectors)

    To support the increased awareness of the modernization of the NSRS, under the auspices of the Federal Geodetic Control Subcommittee, NGS will host a meeting with federal geospatial agencies on Oct. 15, 2025, to discuss the NSRS modernization. The primary objectives of this meeting are to:

    • Increase awareness of the NSRS modernization rollout schedule and engagement strategy, including self-assessment and interaction between official departmental working groups.
    • Within other departments, connect decision-makers to those who accomplish NSRS modernization tasks and designate points of contact to interface with NGS capacity building efforts.
    • Share experiences and strategies among federal agencies concerning NSRS modernization self-assessment and preparation.
    • Gather questions, discuss anticipated challenges and identify opportunities to support each other through this transition.

    It is my understanding that this meeting is open to the public (virtually) for listening and observation. See below for more information on the meeting.

    Federal Geodetic Control Subcommittee Meeting

    • Date: Wednesday, October 15, 2025
    • Time: 1:00 PM – 4:00 PM ET
    Photo:

    I recommend that NSRS users consult guidance from NGS and engage with professional societies that have established working groups to analyze the impact of the new NSRS on geospatial products and services. Getting involved now will help ensure you are prepared when NGS officially adopts the updated NSRS. As Dru Smith, NGS NSRS modernization manager, explained in his webinar titled “NSRS Modernization — Big Steps Forward and What Comes Next” on Aug. 14, 2025, once the initial set of products and services of the modernized NSRS is “official,” the new NSRS becomes “The NSRS,” and its implementation then begins.

    Are you prepared to implement the new NSRS once NGS officially adopts it? Do you have the necessary tools and resources in place to support a smooth transition? This newsletter highlighted several actions that users can take now to ensure they are ready to implement the new NSRS when it becomes official.

  • California updates its spatial reference network

    California updates its spatial reference network

    The California Spatial Reference Center (CSRC) modernized the California Spatial Reference Network (CSRN) on July 31, 2025. The new California Spatial Reference Network is denoted as CSRN Epoch 2025.00. 

    These coordinates changes affect California geospatial users, but the transition process to the new epoch is something that others should understand to prepare for the new, modernized National Spatial Reference System (NSRS), which is expected to be adopted in 2026. As I mentioned in my August 2025 newsletter, NSRS users should proactively assess their geospatial data dependencies and evaluate how adoption of the new datum will affect workflows, datasets and operational decision‑making. 

    The California Spatial Reference System (CSRS) is the official geodetic datum in California, as published by the California Spatial Reference Center (CSRC) according to Public Resources Code (PRC) §§8850–8861. The image below depicts the CSRN. It is rigorously aligned to the current definition of the National Spatial Reference System (NSRS) through a set of coordinate transformations from ITRF2020 to NAD83(2011) as published by the NOAA/NOS National Geodetic Survey (NGS). The California Spatial Reference System (CSRS) is realized by the geodetic coordinates and uncertainties of the CSRN on the date of 2025.00 (January 1, 2025; GPS week 2347, day 3) of 1068 GNSS stations (881 active and 187 defunct stations) in California and at the borders of Arizona, Nevada, Oregon and Baja California. CSRN Epoch 2025.00 NAD83(2011) replaces the previous CSRS Epoch 2017.50 NAD83(2011).

    The latest hybrid geoid model GEOID18 published by NGS was used to compute Global Navigation Satellite System (GNSS)-derived orthometric heights (DCOH) on the North American Vertical Datum of 1988 (NAVD 88) datum in accordance with the California PRC §§8890-8902 (California Orthometric Heights).

    Plot of CSRN (Credit: SOPAC)
    Plot of CSRN (Credit: SOPAC)

    As previously mentioned, the new CSRC Epoch 2025.00 (NAD83 (2011) replaces the previously published CSRC Epoch 2017.5 NAD83 (2011). Readers can obtain the project report that provides technical information about the new realization at the following link: https://sopac-csrc.ucsd.edu/index.php/csrn-epoch-2025-00/ . The website provides web-links to the project report and a table of stations that includes information about the coordinates.  See the image captioned “Excerpt from CSRC Epoch 2025.00 Web Page” for the links to the reports and tables.  The CSRC Epoch 2025.00 realization is aligned with NAD83 2011, Epoch 2010.0.  See the image captioned “Excerpt from Project Report V2” for the summary from the report. I have highlighted some sections of the summary that I thought others would find of interest.

    Excerpt from CSRC Epoch 2025.00 web page.
    Excerpt from CSRC Epoch 2025.00 web page.

    Excerpt from Project Report V2

    Summary

    This report, prepared under California Department of Transportation (Caltrans) Contract No. 52A0157, Task Order 1, documents the modernization of the California Spatial Reference Network (CSRN) by the California Spatial Reference Center (CSRC). This updated realization aligns the CSRN with the North American Datum of 1983 (NAD83 2011, epoch 2010.00).

    The new reference frame, effective on January 1, 2025 (GPS Week 2347, Day 3), is called CSRN Epoch 2025.00 NAD83(2011), referred to for short as CSRN Epoch 2025.00. It replaces the previous adjustment at Epoch 2017.50 and remains a core component of the California Spatial Reference System (CSRS).

    The CSRN is defined by the geodetic coordinates and uncertainties (Table 1) of 1,068 continuous GNSS stations—881 active and 187 inactive or decommissioned—located throughout California and bordering regions in Arizona, Nevada, Oregon, and Baja California, Mexico. As California’s official geodetic reference network under Public Resources Code (PRC) §§8850–8861, all Caltrans surveys using the California Coordinate System of 1983 (CCS83) must reference CSRN control stations or comply with CSRN specifications. The definition and use of CCS83 are governed by PRC §§8801–8819. This new realization is fundamentally tied to the International Terrestrial Reference Frame 2020 (ITRF2020) through the IGb20 coordinates adopted by International GNSS Service (IGS) Analysis Centers. All multi-year processing for this project was performed within this state-of-the-art global reference frame. Furthermore, the CSRN Epoch 2025.00 is rigorously aligned with the National Spatial Reference System (NSRS) maintained by the National Geodetic Survey (NGS). Epoch 2025.00 geodetic coordinates are transformed from ITRF2020 to NAD83(2011) using the NGS Horizontal Time-Dependent (HTDP) utility (Figure 1). The ITRF2020 coordinates (X,Y,Z) of the 1068 CSRN stations are transformed into geodetic coordinates (latitude, longitude and ellipsoidal height), using the GRS80 ellipsoidal parameters (semi-major axis, a = 6378137 m and inverse flattening, 1/f = 298.257 222 101).

    CSRC submitted to the European Petroleum Survey Group (EPSG) definitions for datums, transformations, and coordinate reference systems for Epoch 2025.00 to facilitate unique terminology with associated metadata.

    GPS data (phases and pseudoranges contained in RINEX data files) collected at the CSRN stations from June 10, 1992 to May 17, 2025, and about 300 global tracking stations of the IGS network were re-analyzed in the ITRF2020 reference frame. The complete set of RINEX data and metadata are accessible from the Scripps Orbit and Permanent Array Center data archive.

    The latest hybrid geoid model GEOID18 published by NGS is used to interpolate geoid heights for each of the CSRN stations as the basis of Global Navigation Satellite System (GNSS) derived California Orthometric Heights (DCOH) on the NAVD 88 datum in accordance with the California PRC §§8890-8902 (California Orthometric Heights).

    Figure 1. Reference frames for CSRN Epoch 2025.00 NAD83(2011).
    Figure 1. Reference frames for CSRN Epoch 2025.00 NAD83(2011).

    As provided in the summary of the report, a diagram noted that the ITRF 2020 cartesian (XYZ) coordinates were transformed into NAD83 (2011) cartesian (XYZ) coordinates, and then into local topocentric coordinates (NEU) to obtain the CSRC Epoch 2025.00 NAD83 (2011) coordinates. 

    I downloaded the table of stations with their various coordinates and plotted the differences between the new CSRC Epoch 2025.00 NAD83 (2011) and the previous CSRC Epoch 2017.50 (NAD83 (2011) for stations that were designed as operational stations in 2025.  The following plots depict the difference in coordinates between Epoch 2025.00 and Epoch 2017.50.  One can see that there’s a reason that California needs to periodically update the coordinates of the California Spatial Reference Network.  Some of the horizontal coordinates have changed over 300 mm or around one foot.  The vertical coordinate changes are not as large, but some do shift more than 4 cm.

    Note: The plots do not include newer stations with less than 6 months of solutions (no velocities estimated) and defunct stations (stations in Epoch 2017.50 but no data before January 1, 2025.

    Differences in horizontal coordinates (N, E) between Epoch2025.00 and Epoch 2017.50 northern section.
    Differences in horizontal coordinates (N, E) between Epoch2025.00 and Epoch 2017.50 (northern section).
    Differences in horizontal coordinates (N, E) between Epoch2025.00 and Epoch 2017.50 southern section.
    Differences in horizontal coordinates (N, E) between Epoch2025.00 and Epoch 2017.50 (southern section).
    Differences in vertical coordinates (U) between Epoch2025.00 and Epoch 2017.50 (northern section)
    Differences in vertical coordinates (U) between Epoch2025.00 and Epoch 2017.50 (northern section).
    Differences in Vertical Coordinates (U) between Epoch2025.00 and Epoch 2017.50 (southern section)
    Differences in Vertical Coordinates (U) between Epoch2025.00 and Epoch 2017.50 (southern section)

    The image below provides some statistics about the differences in coordinates between Epoch 2025.00 and Epoch 2017.50.

    Photo:
    Notes: (1) Only includes operational stations in 2025 (2) Does not include newer stations with less than 6 months of solutions (no velocities estimated). (3) Does not include defunct stations: in Epoch 2017.50 but no data before January 1, 2025.

    This newsletter highlighted that the CSRC has adopted a new Public Resources Code–compliant geodetic datum (reference frame) for California: CSRN Epoch 2025.00 NAD83(2011), which replaces CSRN Epoch 2017.50 NAD83(2011). The updated datum incorporates secular (linear) tectonic motions across the North America–Pacific plate boundary, transient motions (such as coseismic and postseismic deformation and fault creep), vertical land motion (subsidence and uplift), and data from new stations established since Epoch 2017.50. Additionally, the new vertical datum provides a comprehensive set of California Orthometric Heights on the NAVD88 datum for all CSRN stations.

    In essence, the CSRC has released three new datums. The first is tied to ITRF2020, the second to NAD83(2011), and the third to NAVD88. Transformation parameters are available between the first two datums. The NAD83(2011)-based datum satisfies California’s Public Resources Code requirements and is the recommended standard for geodetic control in the state. The NAVD88-based datum provides GNSS-derived California Orthometric Heights of 1988 (COH88).

    These new datums will be added to the European Petroleum Survey Group (EPSG) database, the worldwide standard for coordinate reference systems (CRSs) and transformations. Each will receive a unique EPSG code, making it easy to reference and use. This will ensure that CSRN Epoch 2025.00 NAD83(2011), CSRN Epoch 2025.00 (ITRF2020), and COH88 Epoch 2025.00 (NAVD88) can be seamlessly integrated into industry software.

    The CSRC report also noted that NGS has released a beta version of the modernized horizontal and vertical datums for the NSRS: NGS New Datums.

    Once the modernized NSRS is fully published, and in response to the needs of California’s user community, CSRC will continue working to secure resources that support its partnership with NGS and ensure ongoing compatibility with national programs.

  • Changes in OPUS products when the new NSRS is adopted: what does this mean to users?

    Changes in OPUS products when the new NSRS is adopted: what does this mean to users?

    On July 23, 2025, the National Geodetic Survey (NGS) sent a news notice announcing the rollout plan for remaining NSRS modernization products, including OPUS Products Changes, and on June 11, 2025, they sent a news notice to users stating that NGS’s Multi-Year CORS Solution 3 (MYCS3) was released. This newsletter will highlight these two News notices and what they mean to users of the United States National Spatial Reference System (NSRS).

    A colleague recently reminded me that the new NSRS is more than just a technical update — it presents an ideal opportunity to review existing processes and workflows, address current products and process considerations, and strategically plan for future requirements. It is well known that the new NSRS will significantly improve geospatial data accuracy. Improved accuracy and reliability of geospatial data empower management to make more informed decisions and optimize resource allocation. NSRS users should proactively assess their geospatial data dependencies and evaluate how adoption of the new datum will affect workflows, datasets and operational decision‑making. I will provide you with more information at a later date.

    NGS NEWS

    Rollout Plan for Remaining NSRS Modernization products, including OPUS Products Changes

    On June 17, 2025, NGS released the first preliminary products of the modernized National Spatial Reference System (NSRS) for beta testing and feedback. In the coming months, additional products listed below will be made available. As each product is released, it will undergo at least six months of testing preceding the final adoption and implementation of the modernized NSRS.

    The descriptions below supersede previous updates or information shared in NSRS Modernization blueprint documents, plans, or presentations. These products and their status will be described on the Track Our Progress webpage.

    1. The Data Delivery System (DDS) landing page will provide an updated version of the “NGS Map” and “Looking for Benchmarks” pages. This new landing page will allow you to access modernized informational pages about geodetic stations and geodetic marks.
    2. Geodetic station pages will offer an updated version of the current NOAA CORS Network (NCN) station pages. Geodetic mark pages will be updated datasheets, replacing the current ASCII text file version of datasheets. The updated coordinates (reference epoch coordinates) for marks and updated CORS coordinate functions (CCFs) for CORSs in the modernized NSRS will be available through these pages. 
    3. The NGS Coordinate Conversion and Transformation Tool (NCAT) will be updated through multiple versions, currently with state plane coordinates, then later adding support for various geopotential calculations including ellipsoid/orthometric height conversion as well as NADCON (geometric) and VERTCON (orthometric) transformations from the current NSRS to the modernized NSRS.
    4. OPUS-Static will function similarly to today’s tool, but it will operate with the modernized NSRS, including the support of multi-GNSS data. Additionally, the popular function of “sharing” your solution with others (colloquially called “OPUS-Share”) will be retained, but with appropriate caveats that the shared solution should not be used as geodetic control. These shared solutions will be available through the geodetic mark pages of the DDS.

    The following products will not be included in the release of the modernized NSRS. However, plans to replace the services or mitigate gaps are described below.

    • OPUS-Projects 5 will not be included in the modernized NSRS. Instead, NGS will focus on both developing an improved software suite for OPUS, known as OPUS 6, and minimizing any gap in service in which the current OPUS-Projects functionality is not available for users to organize, process, adjust, and submit high-accuracy GPS surveys for use by NGS in expanding and improving the NSRS. As noted above, OPUS-Share will remain available as a means to submit data to NGS.
    • OPUS-Rapid Static (OPUS-RS) will not be included in the modernized NSRS. Instead, the modernized version of OPUS-Static, noted above, will be capable of processing multi-GNSS static data files that are shorter in duration (i.e., less than 2 hours).

    Note: the current OPUS Projects 5 software will be supported until the modernized system is adopted, and a deadline for OPUS-Projects users to submit their surveys for publication will be announced with at least six months’ notice.

    To stay informed about these releases, please subscribe to NGS News. If you have questions, please email [email protected].

    Now, I would like to address the issues associated with July 23, 2025, announcement. This NGS News announced the rollout plan for the remaining NSRS modernization products. I have highlighted several sentences in this announcement that I believe users need to understand to determine the impact on their processes and workflows that are used to generate their products and services.

    The news announcement states that NGS released the first preliminary products of the modernized National Spatial Reference System (NSRS) for beta testing and feedback. My July 2025 GPS World Newsletter highlighted these preliminary products. It mentioned that in the coming months, additional products will be made available.  Each product will undergo at least six months of testing preceding the final adoption and implementation of the modernized NSRS. This seems to be a good process, but users need to understand the complete message.

    The NGS News announcement provides a list of products that will be available and a list of products that will not be available when the new NSRS is adopted. Users need to understand what products will not be available after NGS officially adopts the new NSRS so they can determine what that means to their workflow process and client requirements.  In my opinion, for the new NSRS to be successfully implemented by users, it is essential that all the necessary software tools are available to enable users to submit projects for review, approval, and publication by NGS.  As many of you know, when I worked for NGS, I was the Project Manager of the North American Vertical Datum of 1988 (NAVD 88). That said, from my experience as the NAVD 88 Project Manager, having the appropriate tools available was important for users to implement NAVD 88.  As a matter of fact, NGS accepted and processed vertical control data in both NGVD 29 and NAVD 88 for a period to assist users in the implementation of the new vertical reference datum.

    It is important to note that the NGS News Announcement states that OPUS-Project 5 will not be included in the new NSRS when it is officially adopted. See the below image.

    Credit: NGS

    Since OPUS Projects 5 will not be supported after the modernized system is adopted, users will not be able to submit their projects for review, approval, and publication by NGS like they can do today. NGS does indicate that they will be working on OPUS 6 to “minimize any gap in service.” There are a few questions that I believe should be addressed: (1) What does “minimize any gap in service” mean? Is this one month, one year, or several years?  (2) Why must the new NSRS be adopted before users can submit their projects to NGS for official publication? And (3) Why should users use OPUS-Share when NGS itself advises against relying on OPUS-Share results for establishing geodetic control?  If the federal agencies and surveying community allow the new NSRS to be adopted before OPUS 6 is available or OPUS Project 5 is modified for use in the new NSRS, the only way to get an updated coordinate such as NATRF2022 and NAPGD2022 using NGS process will be to use NGS OPUS-Share products. Again, NGS states that OPUS-Share results should not be used as geodetic control.  See NGS’ statement on OPUS Share below.

    This is NGS’s statement on OPUS-Share: Additionally, the popular function of “sharing” your solution with others (colloquially called “OPUS-Share”) will be retained, but with appropriate caveats that the shared solution should not be used as geodetic control. These shared solutions will be available through the geodetic mark pages of the DDS.

    Using OPUS-Share results that are NOT official NSRS coordinates published by NGS could lead to confusing results and potential lawsuits since NGS does not stand behind the results and recommends NOT using OPUS-Share results for geodetic control. Why would users use OPUS-Share to establish geodetic control when NGS itself advises against relying on OPUS-Share for establishing geodetic control?  OPUS-Share results are not officially submitted to NGS for review, approval, and publication on an NGS Datasheet. I don’t believe this approach will meet the needs of users who require their projects to be reviewed, approved, and published by NGS. What is your opinion? You should let NGS, and others know your thoughts and concerns about NGS’s rollout plan for remaining NSRS modernization products.

    Now for the release of NGS’s Multi-Year CORS Solution 3 (MYCS3).

    NGS MYCS 3 released. (Credit: NGS)
    NGS MYCS 3 released (Credit: NGS)

    First, why did NGS perform the NGS Multi-Year CORS Solution 3 (MYCS3)?  To maintain consistency with the International Earth Rotation and Reference System Service (IERS) and the International GNSS Service (IGS) reference frames, NGS has implemented the new International Terrestrial Reference Frame 2020 (ITRF2020) and IGS20 realizations in the U.S. NOAA CORS Network (NCN). What this means to NSRS users is that NGS has updated the North American Datum 1983 (NAD 83), epoch 2010.0 coordinates for stations in the NOAA CORS Network (NCN). This update is called the Multi-Year CORS Solution 3 (MYCS3).

    In summary, the MYCS3 news notice states the following:

    • The coordinate functions for NOAA CORS Network (NCN) stations are now consistent with ITRF2020,
    • NGS datasheets will display the new NAD 83 coordinates transformed from ITRF2020 coordinate functions,
    • The new NAD 83 coordinates will be referenced to NAD 83 2011 (epoch 2010.0),
    • Position and velocity files will display coordinates/velocities in both NAD 83 and ITRF2020, and
    • The NGS Online Positioning Users Service (OPUS) will begin processing data with NCN control that is consistent with ITRF2020 at the time of measurement; and the results will still be transformed to NAD 83 2011, epoch 2010.0.

    The first question that everyone asks is, what are the changes to the coordinates in my region? And, of course, why was it necessary to do this update now, but that’s a discussion for another day.  I downloaded the data and prepared a few plots and a table to depict the differences between the new and old coordinates.  First, it should be noted that the old NCN coordinates were published in ITRF 2014, epoch 2010.0, and the new NCN coordinates are published in ITRF 2020, epoch 2020.0. So, there will be differences in coordinates because of updates between ITRF2014 and ITRF2020, and because the CORS ITRF 2020 coordinates are published at epoch 2020.0 instead of 2010.0.

    The image below provides the new and old CORS coordinates and velocity information for NOAA CORS Monroe (NCMR). These values can be obtained from NGS CORS website.

    ITRF coordinates for NCMR.
    ITRF coordinates for NCMR. (Credit: NGS)

    The difference between ellipsoid heights is straightforward.  In the example, the difference is 144.357 meters minus 144.345 meters or 0.012 m. The image captioned “Change in Ellipsoid Height in NC based on ITRF 2020” provides the differences between MYCS3 and MYCS2 NAD83 2011, epoch 2010.0 published ellipsoid heights for the CORS in North Carolina.  In other words, this is the change in the NAD 83 2011, epoch 2010.0 ellipsoid height at the CORS after updating to ITRF2020, epoch 2020.  I’ve highlighted the NCMR CORS in the box. As you can see from the plot, there are several CORS in North Carolina that their ellipsoid heights have changed significantly; that is, greater than 20 mm and as large as -89 mm.

    Change in Ellipsoid Height in NC based on ITRF 2020 (units in mm)
    Change in Ellipsoid Height in NC based on ITRF 2020 (units in mm).

    I don’t know about you, but I can’t determine the change in coordinates by looking at XYZ or Latitude/Longitude values.  For the horizontal change I computed the differences in latitude and longitude and converted the results to millimeters. As indicated in the image above, the changes in the horizontal component are typically small; that is, less than a few mm.  There are, however, a few larger changes such as the one at CORS TN1B (which is in Tennessee) that changed 30 mm.

    Change in Horizontal Coordinates in NC based on ITRF 2020 (units mm).
    Change in Horizontal Coordinates in NC based on ITRF 2020 (units mm).

    I suppose for all “practical purposes” the changes are small and shouldn’t impact most survey projects.  Some of the larger changes are probably a good thing because that may mean that the CORS coordinates needed to be updated to account for movement or something else that affected the coordinates. I created a table that provides the minimum, mean, and maximum values in ellipsoid height and horizontal differences.  See the table titled “Differences Between MYCS 3 and MYCS  2 Solutions of NOAA CORS.”  I highlighted the State of North Carolina values.

    Photo:
    Photo:
    Photo:
    Photo:

    So, why is it important to understand these differences?  The NGS Online Positioning Users Service (OPUS) has begun processing data with NCN control that is consistent with ITRF2020 at the time of measurement.  This means that if you compare old projects to new projects, you may find some small differences due to the change in CORS NAD 83 2011, epoch 2010.0 coordinates.  As I previously mentioned, these differences are small and should not affect the results of most survey projects. Although, any difference can lead to someone questioning their results.

    As another example of the changes, the two plots below in the image captioned, “Change in CORS coordinates in Colorado based on ITRF 2020” provides the differences between MYCS3 and MYCS2 NAD83 2011, epoch 2010.0 published coordinates for the CORS in Colorado.

    Change in CORS coordinates in Colorado based on ITRF 2020 Ellipsoid Height Change (units in mm)
    Change in CORS coordinates in Colorado based on ITRF 2020 Ellipsoid Height Change (units in mm).
    Change in CORS Coordinates in Colorado based on ITRF 2020 Horizontal Change (units in mm)
    Change in CORS Coordinates in Colorado based on ITRF 2020 Horizontal Change (units in mm).

    Another difference that I computed using the results from the MYCS3 solution is an estimate of the changes between the current NSRS, that is NAD 83 2011 (epoch 2010.0) and new NSRS, for example NATRF2022, epoch 2020.0.   This is only an estimate but provides a value that users can attain the magnitude of the changes in their local region. The image below depicts the approximate changes in horizontal and vertical components between the current NSRS (NAD 83 2011, epoch 2010.0) and the future NSRS (NATRF2022, epoch 2020.0) based on the CORS in the NCN. (Note that the units have changed to cm.)

    Differences Between ITRF2020 and NAD 83 2011 in NC Horizontal Change (units in cm)
    Differences between ITRF2020 and NAD 83 2011 in NC Horizontal Change (units in cm).
    Differences Between ITRF2020 and NAD 83 2011 in NC Ellipsoid Height Change (units in cm)
    Differences between ITRF2020 and NAD 83 2011 in NC Ellipsoid Height Change (units in cm).

    To demonstrate that these changes vary region by region, I prepared plots depicting the changes in the State of Washington and the U.S. Gulf Coast region. As indicated in the plots, the differences between the current NSRS and the new modernized NSRS will vary from state to state and are significantly different than the current NSRS coordinates. 

    Differences Between ITRF2020 and NAD 83 2011 in Washington State Horizontal Change (units in cm)
    Differences between ITRF2020 and NAD 83 2011 in Washington State
    Horizontal Change (units in cm).
    Differences Between ITRF2020 and NAD 83 2011 in Washington State Ellipsoid Height Change (units in cm)
    Differences between ITRF2020 and NAD 83 2011 in Washington State Ellipsoid Height Change (units in cm).
    Differences Between ITRF2020 and NAD 83 2011 in the Gulf Coast Region Horizontal Change (units in cm)
    Differences Between ITRF2020 and NAD 83 2011 in the Gulf Coast Region Horizontal Change (units in cm).
    Differences Between ITRF2020 and NAD 83 2011 in the Gulf Coast Region Ellipsoid Height Change ( units in cm).

    Differences Between ITRF2020 and NAD 83 2011 in the Gulf Coast Region Ellipsoid Height Change (units in cm).

    This newsletter underscored upcoming OPUS product changes that NGS will implement following adoption of the modernized NSRS, along with updates to CORS station coordinates resulting from the Multi‑Year CORS Solution 3 (MYCS3). It clarified what these changes mean for users of the U.S. NSRS. I also flagged several topics in the NGS News bulletins that warrant further attention, as they are critical for understanding how the modernized NSRS will impact geospatial products and services.  The new NSRS offers a strategic opportunity for users to comprehensively review existing processes and workflows, reassess current products, and proactively plan for future requirements. By auditing geospatial data dependencies now, NSRS users can evaluate how transitioning to the new datum will impact workflows, datasets, and operational decision-making.

    Will you be ready to implement the new NSRS after NGS officially adopts it?  Will you have the appropriate tools available to implement the new NSRS? These are questions that everyone that uses the NSRS should be addressing now.

  • Inside the new NSRS beta tools and a journey through geodetic history

    Inside the new NSRS beta tools and a journey through geodetic history

    This newsletter is going to highlight some history of the Coast and Geodetic Survey and provide the latest information on the National Geodetic Survey (NGS) new National Spatial Reference System (NSRS). First, every year my brother and I get together and travel to visit friends and relatives. He lives in Montana, and I live in North Carolina, so our yearly trips are typically 10 to 14 days long. As in all trips, I look for geodetic marks along the way. This year we traveled to coastal Maine to visit lighthouses and of course eat lobster rolls. We visited 12 Lighthouses along the Maine Coast. Lighthouses have both historical and navigational importance. The lighthouses were essential in guiding sailors through rocky shores. Portland Head Light commissioned by George Washington in 1791 is Maine’s oldest lighthouse and still guides vessels into Portland Harbor. We found NOS benchmark 841 8031 B 1979 on the grounds of this lighthouse. Pemaquid Point Lighthouse is managed by the Friends of Pemaquid Point Lighthouse, a chapter of the American Lighthouse Foundation, and remains an active aid to navigation under the ownership of the U.S. Coast Guard. We could climb up the Pemaquid Point Lighthouse, so I took a photo of the view from the top.

    Portland Head Light (Credit: Dave Zilkoski)
    Portland Head Light (Credit: Dave Zilkoski)

    One of my brother’s requests was to visit the first place in the continental United States to see the sunrise. However, the location of the first place in the continental United States to witness the sunrise depends on the time of year. As indicated in the box titled “First Places to See the Sunrise in the Continental U.S.” Mars Hill is the first place to witness the sunrise in June.

    Mark located on grounds of Portland Head Light. (Credit: Dave Zilkoski)
    841 8031 B 1979 — Mark located on grounds of Portland Head Light. (Credit: Dave Zilkoski)
    Pemaquid Point Lighthouse (Credit: Dave Zilkoski)
    Pemaquid Point Lighthouse (Credit: Dave Zilkoski)
    View from Pemaquid Point Lighthouse (Credit: Dave Zilkoski)
    View from Pemaquid Point Lighthouse (Credit: Dave Zilkoski)

    First Places to See the Sunrise in the Continental U.S.

    • October 7 to March 6: During these months, Cadillac Mountain in Acadia National Park, Maine, holds the distinction of being the first place in the continental U.S. to see the sunrise. Its elevation of 1,530 feet and eastern location make it ideal for early morning views. reddit.com+10nps.gov+10acadiamagic.com+10
    • March 25 to September 18: In the spring and summer, Mars Hill in Aroostook County, Maine, takes the title. Its northeastern position allows it to catch the first rays of sunlight during this period. newengland.com+2en.wikipedia.org+2aa.usno.navy.mil+2

    Around the Equinoxes: Approximately during the weeks surrounding the spring and fall equinoxes, West Quoddy Head in Lubec, Maine—the easternmost point of the contiguous U.S.—experiences the nation’s first sunrise. reddit.com+2en.wikipedia.org+2en.wikipedia.org+2

    That said, when we travel together, we always recover geodetic marks, so we chose to visit Cadillac Mountain even though in June the first place is located on Mars Hill in Aroostook County.  

    As many of you know, I worked for NGS for 35 years so reconning monuments is exciting to me. We found six marks in a radius of about two hundred meters on Cadillac Mountain. We will talk about them in a minute.

    Cadillac Mountain was important to me because from 1833 to 1898, the Coast and Geodetic Survey performed a triangulation project that extended from Calias, Maine, to New Orleans, Louisiana. The project was published as the Eastern Oblique Arc of the United States. The station Mount Desert 1856 that was located on Cadillac Mountain was part of this project. A report published in 1902 describes the Eastern Oblique Arc project and can be downloaded here.

    USCGS Special Publication Number 7. (Credit: USGS)
    USCGS Special Publication Number 7. (Credit: USGS)

    According to the 1902 report, horizontal observations at station Mount Desert 1856 were acquired by Alexander Dallas Bache. That may not mean much to most people, but Mr. Bache was the second superintendent of the Coast Survey and was particularly important to the advancement of geodesy in the United States. As a side note, the Coast Survey was renamed the Coast and Geodetic Survey in 1878. The change reflected the agency’s expanded mission beyond coastal charting to include geodetic surveys of the nation’s interior, prompted by the growing importance of geodesy in its work.

    Bache’s leadership of the U.S. Coast Survey

    In 1843, Bache was appointed superintendent of the United States Coast Survey, succeeding Ferdinand Rudolph Hassler. Under his leadership, the Coast Survey expanded its missions to include hydrography, geodesy, topography, and the printing arts. He initiated geomagnetic studies, directed tide observers to make meteorological observations, and developed mathematical techniques for tide predictions and adjusting triangulation networks. Bache’s administrative skills transformed the Coast Survey into one of the foremost scientific organizations globally, providing critical data for navigation and commerce.

    Alexander Dallas Bache.
    Alexander Dallas Bache

    According to the description of Mount Desert in the 1902 USCGS report, the station was marked by a copper bolt in a ledge (see the box titled “1856 Description of Mount Desert”). The 1902 description of the station on the NGS Datasheet stated that it was a hole drilled in a rock (see the box titled “1902 Description of Mount Desert”). I’m not sure why there is a discrepancy between the two descriptions but in 1931 the Maine Geodetic Survey found the drill hole, and based on measured references to other drill holes in the area that were documented in the original description decided that it was the location of the original station (see the box titled “1931 Description of Mount Desert”).  At that time, a Coast and Geodetic Survey Disk with Reference Marks were installed by the Maine Geodetic Survey.

    A description of Mount Desert from 1856. (Photo: NGS)
    A description of Mount Desert from 1856. (Photo: NGS)
    A Description of Mount Desert from 1902
    A description of Mount Desert from 1902.
    A description of Mount Desert from 1931.
    A description of Mount Desert from 1931.
    A description of Mount Desert from 1931.
    A description of Mount Desert from 1931.

    As I previously stated, we found six marks in the area. The boxes titled “Photos of Mount Desert 1856 and Reference Marks” and “Photos of Other Marks on Cadillac Mountain” provide photos of the monuments we found on Cadillac Mountain.  One may note that the reference mark 2 monument is in worse shape than the reference mark 1 and the Mount Desert monument. The 1944 recovery note stated that reference mark 2 was covered with roadway stone. There was not any stone covering reference mark 2 when I found it. Reference mark 1 is located behind some trees and out of sight of the path.

    When I arrived at the site, there were a group of people looking at reference mark 2. I held a little lecture on the importance of geodetic monuments and how this site was first occupied in 1856; and, of course, I highlighted the importance of geodesy.

    Photos of Mount Desert 1856 and reference marks. (Credit: Dave Zilkoski)
    Photos of Mount Desert 1856 and reference marks. (Credit: Dave Zilkoski)

    I was thrilled to stand in the very spot where Alexander Dallas Bache took geodetic measurements in 1856. [I know—people joke that I need to get a life, all because I get so fired up over geodetic monuments.]

    The box titled “Abstract of Observations at Mount Desert” provides a summary of the directions from Mount Desert to the stations involved in this phase of the project. The box also includes a photo of an instrument, a 75 cm theodolite, which was used to perform the observations. The box titled “Diagram of Network Depicting Epping Base Line” provides a diagram that was included in the 1902 USCGS report.

    As a side note: during the 1970s as a NGS employee, I personally coded abstracts similar to this one to convert archival data into computer-readable form in support of the North American Datum of 1983 (NAD83) project. Once all data were in computer-readable form, they were reviewed for correctness and combined in an adjustment resulting in what is known as NAD 83 (1986).  See the NGS report for some details of the NAD 83 (1986) here.

    Abstract of Observations at Mount Desert (Credit: NGS)
    Abstract of Observations at Mount Desert (Credit: NGS)
    Diagram of network depicting Epping Base Line. (Credit: NGS)
    Diagram of network depicting Epping Base Line. (Credit: NGS)

    The other marks we found on Cadillac Mountain included a US Geological Survey Benchmark – K 24 1934, a bent pipe denoted as Cadillac Ground, and a Department of Interior Geological Mark – Cadillac 1975. All these marks are within a 200-meter radius of each other. My understanding is that Cadillac Ground was established because Mount Desert was obstructed by trees. I have provided weblinks for those that would like more information on these marks.

    Photos of other marks on Cadillac Mountain. From left to right, K 24 1934, Cadillac Ground and Cadillac 1975. (Credit: Dave Zilkoski)
    Photos of other marks on Cadillac Mountain. From left to right, K 24 1934, Cadillac Ground and Cadillac 1975. (Credit: Dave Zilkoski)

    After visiting more lighthouses along the Maine Coast, we traveled back to Boston and visited Waldon Pond and Thoreau’s family home. Why Thoreau you ask? In 2018, the Surveyors Historical Society and NSPS Foundation recognized Thoreau for his work as a surveyor by establishing a commemorative monument at Thoreau’s family farm.

    Thoreau described surveying as a “noble employment” that kept him close to nature: “Surveying … brings you within hearing of [the birds]” – https://www.heritagesurveys.com/famous-surveyors. Surveying and geodesy are indeed noble professions; they provide the foundation for all geospatial products and services.

    Photo of Commemorative Mark at Thoreau’s House. From left to right, Thoreau – A Surveyor, Thoreau Monument and drawing lines. (Credit: Dave Zilkoski)
    Photo of Commemorative Mark at Thoreau’s House. From left to right, Thoreau – A Surveyor, Thoreau Monument and drawing lines. (Credit: Dave Zilkoski)

    Finally, we left Boston for Syracuse to visit my younger brother and sister. I attended the SUNY College of Environmental Science and Forestry (SUNY ESF) which is immediately adjacent to Syracuse University campus. Both of my brothers attended Syracuse University, so we like to walk around campus whenever we visit Syracuse. During our trip to the University, we recovered the monument Thornden 1934. Thornden 1934 was significant to me because I recovered this monument over 50 years ago, as part of a special project that I performed for my geodesy class.

    Thornden 1934 (Credit: Dave Zilkoski)
    Thornden 1934 (Credit: Dave Zilkoski)

    I hope this was not too boring for you, but I real enjoy history and especially the history of the geodetic network of the United States. Today, you can use modern surveying technology to obtain a more accurate coordinate in seconds where it took days to months in the past. That is amazing!

    Now, what is the latest with the modernization of the National Spatial Reference System? On June 17, NGS announced that they incorporated four groups of NSRS modernization products to the NGS beta website.

    Multiple NSRS Modernization Products Published to Beta

    NGS has released the following four groups of products to the NGS beta website to solicit review and feedback from stakeholders as part of the modernization of the National Spatial Reference System (NSRS): (Note: These products are not final and should not be used for anything other than review and testing.)

    North American-Pacific Geopotential Datum of 2022 (NAPGD2022). This datum will replace the North American Vertical Datum of 1988 (NAVD 88) and all other vertical datums for islands in the United States. It will serve as a foundational component of the modernized National Spatial Reference System (NSRS), providing precise definitions for orthometric height (elevation). The release includes the defining grids that collectively make up the datum along with a number of supporting products to visualize the datum.

    Products. All NAPGD2022 products are provided as grids for the following: GEOID2022, DEFLEC2022, GRAV2022.

    Example coordinates. Coordinates and product values are computed for numerous example points throughout NAPGD2022 and provided in a table. NAPGD2022 Experience. Interactive online maps showing NAPGD2022 products for all regions that can be used on a computer or mobile device to query any location.

    Maps of NAPGD2022 products. Static map images of NAPGD2022 products for all regions.New Terrestrial Reference Frames of 2022 for North America (NATRF2022), Pacific (PATRF2022), Caribbean (CATRF2022), and Mariana (MATRF2022) plates. These four geodetic reference frames will replace the North American Datum of 1983 (NAD 83). They will serve as a foundational component of the modernized NSRS, providing precise definitions for geodetic latitude, longitude, and ellipsoidal height.

    Euler Pole Parameters of 2022. All of the new terrestrial reference frames are defined by transformation from the International Terrestrial Reference Frame of 2020 (ITRF2020) using Euler Pole Parameters (EPPs) that model tectonic plate rotation.

    State Plane Coordinate System of 2022 (SPCS2022). A system of map projections for accessing the modernized NSRS. Zone designs have been incorporated into the following beta products and services:

    Zone information tables. SPCS2022 zone definitions, example coordinate computation results, minimum and maximum coordinate values, and minimum coordinate differences with overlapping SPCS2022 zones and with other coordinate systems, provided as interactive tables that can be sorted and filtered.

    SPCS2022 Experience. Interactive online maps showing distortion for all SPCS2022 zones that can be used on a computer or mobile device to get distortion at any location or to view zone definitions.

    Maps of SPCS2022 zones and distortion. Static map images of SPCS2022 zone layers, number of zones, and distortion with performance statistics.

    NGS Coordinate Conversion and Transformation Tool (NCAT). This version can be used to perform SPCS2022 coordinate conversions at any location for all SPCS2022 zones. Later beta versions will include the ability to transform between reference frames and vertical datums.

    Products found on the NGS beta website are preliminary releases that are for testing and evaluation only; they are not final products nor do they contain any authoritative NGS data or tools. To provide feedback on any of the content on this site, please email [email protected].

    Everyone should review these products and provide their feedback to NGS. That said, my April 2025 newsletter highlighted the NAPGD2022 Alpha product that was moved to the Beta site. The Beta product is like the Alpha product, but it does not have an option for an interactive computation. The Interactive Computation Option provided essential information about NAPGD2022 and would be helpful to geospatial users for obtaining a better understanding of the differences between NADGP2022 orthometric heights and NAVD 88, and GEOID2022 geoid heights and hybrid GEOID18 geoid heights. My April 2025 newsletter highlighted the interactive computation option.

    Alpha interactive computation page (Credit: NGS)
    Alpha interactive computation page (Credit: NGS)
    Alpha interactive computation page (Credit: NGS)

    As noted in my April 2025 newsletter, I downloaded the data and created my own maps to better highlight local variations. Although users can still view the original via the interactive online map, this personalized version offers clearer insights.

    Here are several of my comments on the Beta products based on my preliminary review:

    • The NAPGD2022 difference map (NAPGD2022 minus Historical in meters) uses 25 cm intervals, which are too coarse to reveal the finer local variations between published benchmarks accurately.
    • The NAPGD2022 Difference map should have an overlay of the marks used in the creation of the difference map. This would allow users to identify marks in their region of interest. Clicking on a mark should link to the NGS datasheet and Passive Mark Page.
    • The beta page for NATRF2022, PATRF2022, CATRF2022, and MATRF2022 is not particularly helpful for everyday geospatial users. There should be an Interactive Computation Option to enter NAD83 (2011), epoch 2010 coordinates where the routine transforms the coordinates into ITRF 2020, epoch 2020, as well as estimates in the new terrestrial reference frames – NATRF2022, CATRF2022, PATRF2022, and MATR2022.
    • Both the State Plane Coordinate System of 2022 (SPCS2022) and The NGS Coordinate Conversion and Transformation Tool (NCAT) are good tools for users to obtain an understanding of the differences and changes in the SPCS especially for their State. That said, like above, there should be an option to enter NAD83 (2011), epoch 2010 coordinates where the routine will transform the coordinates into ITRF 2020, epoch 2020, as well as estimates in the new terrestrial reference frames – NATRF2022, CATRF2022, PATRF2022, and MATR2022. The routine does have a note that states users can transform their coordinates using HTDP, but NGS should incorporate this process in the NCAT beta product.
      • Note from Beta NCAT product: This beta version of NCAT supports beta State Plane Coordinate System of 2022 (SPCS2022) but not transformations between reference frames or geopotential datums. NAD 83 latitude and longitude can be used as input, but the output coordinates will differ horizontally from actual SPCS2022 by up to a few meters, depending on location (likewise for UTM and USNG). If NAD 83 ellipsoid heights are used, the linear distortion and combined factor will differ from SPCS2022 values by a small amount, within ±0.3 parts per million (ppm). To reduce these differences, NAD83 epoch 2010.0 coordinates can first be transformed to ITRF2020 epoch 2020.0 using the Horizontal Time-Dependent Positioning (HTDP) tool.

    I plan to provide these comments to NGS through their feedback email process. Everyone should take time to review these products and provide your feedback to NGS. Remember, NGS placed these four groups of products on the NGS beta website to solicit review and feedback from stakeholders as part of the modernization of the National Spatial Reference System (NSRS) process. Users should review these Beta products and consider two questions:

    1. Do these products provide sufficient information and detail for documenting how I will deliver my products and services under the new NSRS?

    2. Do I need additional information or tools from the NGS to better understand the changes and impacts of the new NSRS?

    Your feedback will help NGS improve the Beta products.

  • Evaluating your constraints in a GNNS network adjustment

    Evaluating your constraints in a GNNS network adjustment

    My previous newsletter highlighted a National Geodetic Survey (NGS) webinar held on April 25, 2025, titled “Design of Networks Using NOS NGS 92,” given by Dave Zenk, NGS northern plains regional advisory.

    [Authors note: Dave Zenk told me that he is retiring from the National Geodetic Survey on May 31, 2025. Dave’s presence will be deeply missed. His dedication and spirit have left a lasting impact on NGS’s products and services. I hope his retirement is filled with joy, relaxation, and new adventures.] 

    In addition to Dave Zenk’s retirement, several other NGS Regional Geodetic Advisers have retired or left NGS employment over the past several months. Click here for a list of the current advisors, along with the names of interim contacts handling inquiries for those advisors who have retired or departed from government service.

    As previously mentioned, Dave showed a well-presented outline of the tables that users need to be familiar with when using OPUS Projects to process and submit GNSS projects to NGS for publication. It should be noted that users submitting data to NGS must follow the guidelines outlined in NOS NGS 92.

    I found the webinar to be very informative, and I would encourage all users of OPUS Projects to download the presentation. During the webinar, Zenk briefly mentioned three items that I believe deserve more explanation for anyone using OPUS Project. This newsletter will address the following topics in more detail:

    • The mark’s classification — primary, secondary, and local — will not be included on the NGS datasheet, but the local and network accuracy from the project will be provided on the datasheet. What does this mean to someone who’s using the mark in their project?
    • OPUS Project uses the F-statistic test to determine if the appropriate constraints were imposed during the horizontally and vertically constrained adjustments. Why does OPUS Project use this statistic?
    • The Constraint Ratio (CR) test, computed by OPUS Projects, provides a method for identifying which coordinates should be constrained and which should not be considered for constraints in the final horizontally and vertically constrained adjustments. What’s the best way to use this table?

    First, the presentation discussed the tables that described the procedures for establishing three different mark classifications — primary, secondary and local. It also mentioned that the classification will not be included on the NGS datasheet but the local and network accuracy from the project will be provided on the datasheet. See the image below.

    Photo:
    Photo: NGS website

     What does this mean to someone who’s using the mark in their project? Since the NGS data sheet will provide the network and local accuracy from the project, users can determine if the accuracy value of the mark meets the requirements of their project. In my opinion, the network and local accuracy from the project provide a better indication and understanding of the level of trust of the published coordinate.

    As previously mentioned, anyone submitting a GNSS project to NGS for publication must adhere to the NOS NGS 92 guidelines. During the presentation, Zenk provided several examples that depicted correct network designs. I would encourage everyone to download the NOS NGS 92 document and Zenk’s presentation to gain an understanding of the classifications and the network design requirements to meet a particular classification.

    Photo: NGS website
    Adhere to NOS NGS 92 guidelines (Photo: NGS website)

    Anyone who submits an OPUS Project to NGS for publication knows that the constrained adjustments must meet the requirements of the F-statistic test. So, what is this test, and why does OPUS Project require this statistic? Essentially, it is a method of verifying whether the appropriate constraints were applied during the horizontally and vertically constrained adjustments. The F-test evaluates the ratio of two variances; that is,

    Photo:

    The F-test checks whether this ratio is significantly different from 1, which would suggest the models have significantly different fits to the data. The result is compared against the critical value from the F-distribution based on the degrees of freedom from the constrained adjustment and the degrees of freedom from the minimally constrained adjustment, and a chosen significance level alpha (e.g., 0.01).  NGS OPUS Project uses an alpha level of 0.01% or 99% confidence level.

    Photo:
    Definition of the F-test (Photo: Wikipedia)

     
    The following is an excerpt on the F-test from NGS’s Online OPUS Project Guide  – (Section 12.7.3.2. Analyzing the Horizontal Constrained Adjustment):

    Once the adjustment has been deemed acceptable i.e. all shifts and residuals are reasonable, the F-test should pass. The F-test is a statistical test that helps determine if the variance (variance of unit weight) from a fully constrained adjustment is significantly different from the variance (variance of unit weight) of a minimally constrained adjustment. The variance of unit weight is a critical statistic and should be looked at carefully when evaluating adjustment results. If the fully constrained adjustment fits well with all selected control (the constraints), the value of the variance of unit weight should be close to 1.0. The F-test is performed using a 99% confidence level.

    So, if the constrained adjustment statistics differ significantly from the minimally constrained adjustment, then there could be an issue with the constraints.  Of course, this is assuming that the minimally constrained adjustment variance of unit weight indicates that all data outliers have been eliminated.  So, why are constraints important?

    OPUS Project first calculates GNSS coordinates in a minimally (free) network adjustment, which defines relative positions but not their absolute placement in space.  Without constraints the entire network can float and/or rotate.

    Constraints are important in GNSS network adjustments because they:

    • Anchor the network in a geodetic datum; in this case, NAD 83 (2011), epoch 2010.0.
    • Ensure a unique and stable solution that reflects the physical world.
    • Make the network useful for engineering, mapping, and scientific purposes.

    Control point coordinates (from previous surveys or known datums) often have inherent errors or uncertainty. Constraining coordinates exactly assumes zero error, which is rarely true.   Weighted constraints let you assign a realistic level of trust to known published coordinates by using error estimates. OPUS Project applies weighted constraints based on input error estimates (OPUS Project denotes these as sigmas of the coordinates), which allow for minor deviations in the constrained coordinates. The weighted constraint methodology provides flexibility to network adjustments by recognizing that published coordinates have some uncertainties and allows constraints to take on small corrections leading to more accurate and consistent network solutions. Although, it should be noted that the adjusted coordinates of the constraints from the final horizontally constrained adjustment are not updated in the NGS database even though there are minor deviations to their final adjusted values.

    After performing a least squares adjustment using the weighted constraints, the F-test helps to ensure that the appropriate coordinates are constrained with the appropriate error estimates. The following is an excerpt from the OPUS Project Online User Guide – (Section 12.7.3.2. Analyzing the Horizontal Constrained Adjustment):

    If the F-test fails, it is due either to the errors (sigmas) of the constraints being overly optimistic (too small) or the constrained coordinates not agreeing with the observations (causing excessively large shifts of the constrained coordinates). Failure of the F-test does not automatically mean the constrained adjustment is bad. It is a flag that indicates there may be a problem with the constraints, and that they should be investigated. In addition, the F-test assumes of a normal (“bell-shaped”) probability distribution of the residuals. Networks with a distribution that is significantly non-normal may fail for that reason, even when a constrained adjustment is acceptable.

    if your adjustment fails the F-test, what do you do?  How do you determine which constraint or constraints should be unconstrained?  OPUS Project provides some information about the constraints that can be helpful in determining a bad constraint.  The CR test, computed by OPUS Projects, provides a method for identifying which coordinates should be constrained and which should not be considered for constraints in the final horizontally and vertically constrained adjustments.  What’s the best way to use this table?  The box titled “Constraint Ratio” from NGS’s Online OPUS Project User Guide — (Section 12.7.3.2. Analyzing the Horizontal Constrained Adjustment) provides a good explanation with an example of using the constraint ratio table (12.7.3.2. Analyzing the Horizontal Constrained Adjustment).  Basically, this statistic highlights coordinate shifts that are significantly larger than expected based on the sigma provided by the user.  That is, coordinates that have a very small sigma should not be expected to change as much as coordinates with a very large sigma.  The CR value is compared to a critical value of 3.0, which corresponds to a t-statistic at the 99% confidence level.  Therefore, any constraint ratios greater than three should be investigated and are candidates to be unconstrained (see the box titled “Constraint Ratio”).

    Constraint Ratio

    If the F-test fails, it is possible that some constraints need to be freed up. It might be the case where some of the shifts are too large. The CR test provides a way of identifying where the bad shift might be. The CR is essentially a Students T Test, with the absolute value of the shift between the adjusted, constrained coordinates and the published coordinates, divided by the sigma (σ, or standard deviation) used to constrain the station. It is computed for each component (north, east, and height):

    Photo:

    OP provides the CR for all marks in the final table in the output summary given in the body of the email or in the Processing Report (.txt), as shown below in Fig. 12.21.

    Fig. 12.21 Constraint Ratio Test as seen in the Processing Report of the Horizontal Constrained Adjustment. (Photo: NGS)
    Fig. 12.21 Constraint Ratio Test as seen in the Processing Report of the Horizontal Constrained Adjustment. (Photo: NGS)

    Computed CRs are compared to the critical value or 3.0, corresponding to a T-statistic at a 99% confidence level. If the value of CR is greater than 3.0 for any of the three components, that indicates that there may be a problem with the constrained station.

    I find these statistics very helpful when determining which coordinates should be constrained in the final adjustments.  I hear that some users select all possible constraints and then start releasing marks based on the CR table.  That certainly is one way of doing it but could be time-consuming and confusing.  That said, the first thing I do is compare the minimally constrained adjusted coordinates to the published coordinates to determine if there are any obvious outliers.    This has been helpful to me in large GNSS projects located in subsidence regions such as the Harris-Galveston, Texas, region of the United States.

    One final note on OPUS Project

    On May 22, 2025, NGS issued a notice to users, announcing the implementation of the International Terrestrial Reference Frame 2020 (ITRF2020).  The announcement provided the following information addressed to all Active OPUS Project Users.

    Active OPUS-Projects Users,

    In early June, NGS will implement the new International Terrestrial Reference Frame 2020 (ITRF2020) and IGS20 realizations in the U.S. National Spatial Reference System (NSRS) in order to maintain consistency with the International Earth Rotation and Reference System Service (IERS) and the International GNSS Service (IGS) reference frames. This results in updated North American Datum 1983 (NAD 83) coordinates for stations in the NOAA CORS Network (NCN), kept at epoch 2010.0. This update is called the Multi-Year CORS Solution 3 (MYCS3), and it follows NGS’s MYCS2 effort from 2018.

    OPUS-Projects users with active projects are advised that open projects will need to be reprocessed from the beginning in ITRF2020. 

    If projects are close to completion, users have the option of submitting them to NGS before the transition using the currently published NAD83(2011/MA11/PA11) coordinates transformed from ITRF2014. The deadline for submissions is June 6, 2025 for those wishing to take this route.

    If you have questions, please contact [email protected].

    Above, I bolded several sentences that will be important to users currently performing projects using OPUS Projects.  That is, all projects not submitted by June 6, 2025, will need to be reprocessed from the beginning in ITRF2020.  

    Users should continue to check NGS’s website for announcements regarding the transition from the alpha site to the beta site. Future newsletters will address the Multi-Year CORS Solution 3 (MYCS3) and will highlight the beta products as they are released.

  • AAGS launches geodetic surveying certificate: Key updates from joint NGS/NSPS/AAGS meeting

    AAGS launches geodetic surveying certificate: Key updates from joint NGS/NSPS/AAGS meeting

    As president-elect of the American Association for Geodetic Surveying (AAGS), I participated in a joint quarterly meeting with the National Geodetic Survey (NGS), the National Society of Professional Surveyors (NSPS) and AAGS on April 25.

    I invite you to visit the AAGS website and consider joining our monthly board meetings, which are held on the second Tuesday of each month. All are welcome to attend. If you are interested, email me at [email protected] to be added to the attendee list.

    Now, for some updates from the joint quarterly meeting.

    During the meeting, I provided an update on the Certificate for Geodetic Surveying program, which has been under development by AAGS and is expected to be available by the end of the year. The program is designed to meet the needs of surveyors and others that perform spatial analyses and computations using geodetic methods.

    Tim Burch, executive director of the National Society of NSPS, wrote the following in an April 23, 2025, xyHt article:

    “To the average professional surveyor, the term “geodesy” does not exist in their everyday conversations about the business. While the use of state plane coordinates has expanded greatly with the development of GPS/GNSS receivers and RTK/RTN connectivity, the mathematics and “black magic” of geodesy remains an enigma to most of the profession.

    However, the ongoing progression of technology within surveying instruments has expanded the need for understanding how geodesy works. Our practitioners are faced with expanding their knowledge and expertise of geodesy and thus have put a new challenge on them to find teachers and/or mentors to provide training on the datums and techniques.”

    This is exactly what AAGS is attempting to do with the Certificate for Geodetic Surveying program. The information below includes the program description and content. AAGS has developed a set of questions that will determine if an individual has demonstrated a minimum competence in understanding and applying geodetic surveying concepts. AAGS is working with NSPS, who will be administrating the program for AAGS. The status and updates of this program are provided at the AAGS Monthly Board meetings. Come join us to hear more about the program and other AAGS activities.

    Certification for Geodetic Surveying

    Program description and content. Certification for Geodetic Surveying is official recognition that a person has demonstrated to the satisfaction of the Certification for Geodetic Surveying Board that he or she is minimally competent to perform spatial analyses and computations using geodetic methods.  It is not intended to certify scientists performing research in geodesy.  Rather, it is for individuals who use geodetic concepts and techniques to solve practical problems as a part of performing their work.  Typical practitioners include geodetic surveyors, geodetic/geomatics engineers, geospatial software developers, geographic information systems (GIS) professionals, and geospatial data managers.  The focus is more on the use of applied geodetic methods than with a particular field.  A person who has obtained the Certification for Geodetic Surveying is one who has demonstrated minimum competence.  In this context, “minimum competence” is a combination of working knowledge and familiarity with geodetic concepts that shows the ability to understand and solve applied practical geodetic problems as normally encountered in modern geospatial practice.  Importantly, this includes an understanding of one’s limitations in solving such problems. 

    The Certification for Geodetic Surveying Board will identify the depth of knowledge required to achieve minimum competence for Geodetic Certification in the following areas:

    • Geometric geodesy
      •  Reference frames, reference systems, geometric datums, and realization strategies
      • Characteristics of modern reference systems, including NAD 83, WGS 84, ITRF, and IGS
      • Transformations between datums, both modern and historic
      • Geodetic, projected, and local geodetic horizon coordinate systems
        • Direct and inverse problems for geodesics and map projections
        • Reference ellipsoids, radii of curvature, and types of geodetic and projected distances
        • Reductions, conversions, and relationships between coordinate systems
        • Transformations used to create “localization/calibration” coordinate systems
    • Physical geodesy
      • Gravity, “the” geoid, gravimetric and “hybrid” geoid models, physical height systems, deflection of the vertical
      • Vertical geodetic datum definitions and transformations
      • Types of heights and their relationships; conversions between the various types
      • Terrestrial methods for vertical, horizontal, and 3-D positioning
        • Geodetic leveling and height determination; leveling instrumentation and corrections
        • Modern 3-D terrestrial methods and instruments, including total stations and scanners
        • Familiarity with historical methods such as triangulation, trilateration, and geodetic astronomy
    • Accuracy and error
      • Positional error estimation and uncertainty propagation; statistics and probability theory
      • Characterization using network and local accuracies, error ellipses, and confidence levels
    • Temporal aspects
      • Plate tectonics (both steady-state and episodic); plate-fixed versus no-net rotation reference systems; subsidence; isostatic adjustment; tidal deformation
      • Time-dependent transformations between reference systems
    • Global Navigation Satellite Systems (GNSS)
      • Instrumentation; system architecture; signal structure; error budget
      • Methods for position determination, including by pseudorange, differential correction, carrier-phase differencing, and precise point positioning
    • Geodetic survey networks
      • Design, adjustment, and analysis of GNSS and terrestrial geodetic survey networks
      • Formulation and solution of least-squares network adjustments
    • Standards and guidelines
      • Official standards, specifications, and guidelines for geodetic control, positioning, and accuracy
      • The US National Spatial Reference System and similar systems elsewhere

    Many of you are probably aware of the actions taken by the current administration to reduce the size of the U.S. federal workforce, these actions may affect all users of U.S. geospatial products and services.  NGS is not exempt from these actions; recently, they have lost many employees either though leaving service voluntarily, retiring earlier than planned, or having been terminated because they were still in the probation period of their employment. NGS leadership did not provide any details on changes in personnel; only time will tell what the loss of personnel will have with the agency in the future. That said, NGS’s plans still include transitioning the modernized NSRS Alpha Site to a Beta Site this year. The current alpha site has four products — State Plane Coordinate System. SPCS2022, NGS Coordinate Conversion and Transformation Tool (NCAT), Euler Pole Parameters (EPPs) and The North American-Pacific Geopotential Datum of 2022. My understanding is that all four of these alpha products will be transitioned to beta products sometime in 2025. Some may have limited options in the beginning. 

    During this period, the beta site will provide the content, format and structure of data and products that should not change much from the final product. There could be minor changes detected during the beta phase, but users should not anticipate large significant changes. That said, that is why you have a beta phase before production. It is important for users to access the beta products and identify any issues or concerns and provide feedback to NGS. Future newsletters will highlight the beta products as they are released.

    NGS Alpha Site (Photo: NGS website)
    NGS Alpha Site (Photo: NGS website)

    Finally, I would like to highlight a NGS webinar held on April 25, “Design of Networks Using NOS NGS 92.”  Dave Zenk, NGS Northern Plains Regional Advisory, gave a good presentation outlining the tables that users need to be familiar with using OPUS Projects to process and submit GNSS projects to NGS for publications. The webinar provided a few examples to explain the concepts.  Users can download the webinar from NGS webinar website.

    Design of networks using NOS NGS 92. (Photo: NGS website)
    Design of networks using NOS NGS 92. (Photo: NGS website)

    I found the webinar to be very informative, and I would encourage all users of OPUS Projects to download the presentation.  During the webinar, Dave briefly mentioned three items that I believe deserve more explanation for anyone using OPUS Project. I will address the following topics in more detail in future newsletters:

    • The mark’s classification — primary, secondary, and local – will not be included on the NGS datasheet but the local and network accuracy from the project will be provided on the datasheet.  What does this mean to someone that’s using the mark in their project?
    • OPUS Project uses the F statistic test to determine if the appropriate constraints were imposed during the horizontally and vertically constrained adjustments.  Why does OPUS Project use this statistic?
    • The Constraint Ratio (CR) test computed by OPUS Projects provides a way of identifying which coordinates should be constrained and which should not be considered for constraints in the final horizontally and vertically constrained adjustments. What’s the best way to use this table?

    Again, I would like to invite you to check out the AAGS website and consider participating in AAGS monthly Board meetings. If you are interested in attending the meeting, send an email to me at [email protected]. 

    Finally, users should continue to check NGS’s website for the announcement of the transition from the alpha site to the beta site. Future newsletters will highlight the beta products as they are released.

  • NAPGD2022 is coming soon: How will the new geopotential datum impact products and services?

    NAPGD2022 is coming soon: How will the new geopotential datum impact products and services?

    My January 2025 GPS World newsletter mentioned that the National Geodetic Survey (NGS) made several updates to the North American-Pacific Geopotential Datum of 2022 (NAPGD2022) products and that these updates are now available on the NGS alpha site. NGS held a webinar on Jan. 9, 2025, to discuss NAPGD2022 and explain the product updates. I highlighted the NGS Alpha site and GEOID2022 — a product of the NAPGD2022 — in my July 2024 newsletter.

     This newsletter will highlight the NAPGD2022 alpha site and the components on the Alpha site — GEOID2022, DEFLEC2022, DEM2022 and GRAV2022. See below for a description of the site.

    Photo:
    Photo: NGS alpha website.

    NGS users of the new National Spatial Reference System (NSRS) should determine the impact on their products and services. For example, the effect of using NAPGD2022 orthometric heights instead of the North American Vertical Datum of 1988 (NAVD 88) on flood plain maps and FEMA elevation certificates.

    I have experience dealing with the impact of products and services changing from one national vertical datum to another. When I worked for NGS, I was the Project Manager of NAVD 88. The adjusted heights from the NAVD 88 general adjustment were officially published on June 15, 1991. Performing the adjustment of NAVD 88 was a relatively simple task compared to implementing of NAVD 88 in geospatial products and services in the United States. I wrote articles and talked about the change in the datum from the National Geodetic Vertical Datum of 1929 (NGVD 29) to NAVD 88 at surveying and mapping conferences several times a year during the decade before the completion of the adjustment. Many users were still surprised by the change and the impact on their products and services. It’s a little different today because there are more ways of getting the word out in today’s digital world, such as webinars, Zoom meetings and digital magazines. That said, users still need to participate in webinars and Zoom meetings and read digital articles to understand the changes to geospatial products and services.

    The NAPGD2022 alpha site can be accessed here.

    Photo:
    Photo: NGS

    Users can download gridded files of the models to create their own routines to analyze the models in their region.

    Photo: NGS
    Photo: NGS

    The site provides an option for users to perform single point interactive computations.

    Single point interactive computations. (Photo: NGS)
    Single point interactive computations. (Photo: NGS)

    The differences between the ITRF 2014 (epoch 2010.0) coordinate and ITRF 2020 (epoch 2020.0) in North Carolina are not very large. Still, I used NGS’s HTDP tool to transform the North Carolina Monroe CORS (NCMR) ITRF 2014 (epoch 2010.0) coordinates to ITRF 2020 (epoch 2020.0) and then entered the transformed values into the interactive tool. See the images “HTDP Output for NCMR” and “Interactive Computation Page” for an example of the output of the single-point interactive computation tool.

    HTDP output for NCMR. (Photo: NGS)
    HTDP output for NCMR. (Photo: NGS)
    Photo: NGS
    Photo: NGS

    I have highlighted the NAPGD2022 orthometric and dynamic heights for NCMR CORS. I downloaded the latest NGS datasheet for the North Carolina Monroe CORS (NCMR) to obtain the published NAVD 88 height. See the image below. 

    NGS data sheet for Manroe CORS. (Photo: NGS)
    NGS data sheet for Manroe CORS. (Photo: NGS)

    In my example, the difference between the NAPGD2022 and NAVD 88 orthometric height is -0.26 meters (174.40 m – 174.66 m). It should be noted that the tool also provides a dynamic height for the mark. Dynamic heights are used by the International Great Lakes Datum (IGLD). My August 2021 GPS World Newsletter provides more information on the update to the IGLD 85 and dynamic heights. The interactive computation page tool also provides the GEOD2022 value for the mark. The difference between GEOID2022 and GEOID18 for the mark is -0.112 meters (-31.428 minus -30.316).

    The alpha site provides an option to use an interactive online map that allows users to access GIS maps that depict individual models.  I have highlighted the five layers on the box titled “NAPGD2022 Interactive Online Map” – GEOID2022, SDEFLEC2022, GRAV2022 (RBA), Geoid Differences, and NAPGD2022 Differences.

    Photo:NAPGD2022 interactive online map. (Photo: NGS)
    NAPGD2022 interactive online map. (Photo: NGS)

    To demonstrate the online maps, I clicked on the layer titled “NAPGD2022 Difference” located in the upper right corner of the of the map. The image below provides a description of the layer.

    Photo: NGS
    Photo: NGS

    Users can click on the map, and the pop-up provides information about the location. In the example below, the popup provides the difference between the NAPGD2022 orthometric height and the NAVD 88 height.

    The difference between NAPGD2022 orthometric height and NAVD 88 height. (Photo: NGS)
    The difference between NAPGD2022 orthometric height and NAVD 88 height. (Photo: NGS)

    Additional information about a layer is provided on the lower left side of the map page.

    Additional information for NAPGD2022 difference. (Photo: NGS)
    Additional information for NAPGD2022 difference. (Photo: NGS)

    NGS’ online maps didn’t depict the details I wanted to visualize, so I downloaded the data and created my own maps.

    I provided a couple of examples of the differences between NAPGD2022 and NAVD 88 below: one for North Carolina and one for Colorado. As you can see from the plots, there are significant relative differences in mountainous regions (western North Carolina and western Colorado), and a lot of local variation across the state.

    Photo:Differences between NAPGD 2022 orthometric heights and NAVD 88 in North Carolina (2 cm contour intervals). (Photo: Dave Zilkoski)
    Differences between NAPGD 2022 orthometric heights and NAVD 88 in North Carolina (2 cm contour intervals). (Photo: Dave Zilkoski)
    Differences between NAPGD 2022 orthometric heights and NAVD 88 in Colorado (5 cm contour intervals). (Photo: Dave Zilkoski)
    Differences between NAPGD 2022 orthometric heights and NAVD 88 in Colorado (5 cm contour intervals). (Photo: Dave Zilkoski)

    I used the same process to determine the differences between GEOID2022 and GEOID18. See the images titled “Differences between GEOID2022 and GEOID18 in North Carolina” and “Differences between GEOID 2022 and GEOID 18 in Colorado.”  Again, it should be noted that there is a lot of variation across the state.

    Differences between GEOID2022 and GEOID18 in North Carolina (2 cm contour intervals). (Photo: Dave Zilkoski)
    Differences between GEOID2022 and GEOID18 in North Carolina (2 cm contour intervals). (Photo: Dave Zilkoski)
    Differences between GEOID 2022 and GEOID 18 in Colorado (5 cm contour intervals). (Photo: Dave Zilkoski)
    Differences between GEOID 2022 and GEOID 18 in Colorado (5 cm contour intervals). (Photo: Dave Zilkoski)

    In summary, in a few months, NGS will be releasing a Beta version of the new terrestrial reference frames and geopotential datum. This newsletter highlighted the NAPGD2022 alpha site and the components on the Alpha site — GEOID2022, DEFLEC2022, DEM2022, and GRAV2022. I did a 4-part series in my GPS World newsletters in 2017 on the products of NAPGD2022 (June 2017, August 2017, October 2017 and December 2017).

    NGS’s Jan. 9, 2025, webinar discussed the North American-Pacific Geopotential Datum of 2022 (NAPGD2022) Alpha website and explained the recent product updates. I would encourage users to download the video and presentation for more details. Now is the time for surveyors to learn about the new, modernized National Spatial Reference System. NGS publicly given presentations collected for public viewing can be downloaded from the following website: https://geodesy.noaa.gov/web/science_edu/presentations_library/.