New Datums – New Coordinates – New Heights-New Datums – New Coordinates

Video Transcription

Video Summary

This online education session, hosted by ACEC's Coalition of Professional Surveyors, addresses the significant update to the U.S. national coordinate system—the most substantial change in over 30 years—led by the National Geodetic Survey (NGS). David Doyle, former Chief Geodetic Surveyor with over 40 years of experience, explains that the modernization affects how horizontal and vertical positions, heights, and geospatial data are defined and shared, impacting surveying, engineering, GIS, infrastructure, and construction industries.<br /><br />Key points include the transition from NAD 83 and NAVD 88 datums to new reference frames with improved accuracy, centered on the Earth’s geocenter rather than local survey marks. The new system aligns with the International Terrestrial Reference Frame (ITRF 2020) and introduces four regional reference frames based on tectonic plates. Horizontal offsets of about 1.5 meters exist between old and new datums, which the update seeks to eliminate using GNSS technologies and continuously operating reference stations (CORS).<br /><br />Vertically, the update replaces leveling-based datums with a geoid model (GEOID 2022) derived from comprehensive gravity measurements, offering roughly 1 cm accuracy nationwide and unifying datums across all U.S. regions, including islands previously without leveling data. The update also removes the U.S. Survey Foot from state plane coordinate systems and simplifies zones in states like Ohio, standardizing coordinate conversions.<br /><br />Doyle emphasizes the importance of metadata accuracy, epoch tagging for coordinates, and understanding transformation uncertainties—especially critical given FEMA's continued use of older datums for floodplain mapping. The National Geodetic Survey provides tools like NCAT and NAPGD 2022 for transformations and urges professionals to be proactive in supporting community transitions during this technological shift.

Keywords

U.S. national coordinate system update

ACEC Coalition of Professional Surveyors

National Geodetic Survey

NAD 83 and NAVD 88 transition

International Terrestrial Reference Frame (ITRF 2020)

regional tectonic plate reference frames

GNSS and CORS technologies

GEOID 2022 geoid model

removal of U.S. Survey Foot

metadata accuracy and epoch tagging

NCAT and NAPGD 2022 transformation tools