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

New Datums – New Coordinates – New Heights Slides

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This document from the American Council of Engineering Companies, dated September 10, 2025, authored by Dave Doyle, outlines upcoming changes and challenges in geodetic datums used across the United States and territories. It highlights issues with the current NAD83 horizontal datum and NAVD88 vertical datum, noting NAD83’s lack of true geocentricity (~1.5 meters offset in continental U.S.) and insufficient accounting for positional velocities due to tectonics. NAVD88 relies on outdated passive control benchmarks, many unreleveled for 30-40 years, failing to adequately model local vertical land movements caused by processes such as glacial isostatic adjustment, subsidence, or sediment compaction.<br /><br />The document introduces new datums set to replace NAD83 and NAVD88 in late 2027 or early 2028. NAD83 will be succeeded by the North American Terrestrial Reference Frame (NATRF2022) and region-specific frames like Caribbean (CTRF2022) and Pacific (PTRF2022), all referenced to ITRF2020. NAVD88 will be replaced by the North American-Pacific Geopotential Datum 2022 (NAPGD2022), based on a new gravimetric geoid model GEOID2022, allowing for more accurate orthometric heights without reliance on physical benchmarks.<br /><br />It explains the alignment with international standards from the International Earth Rotation and Reference System Service (IERS) and associated services for GNSS, laser ranging, DORIS, and VLBI. The document details coordinate comparisons, tectonic plate velocities, and transformations between old and new datums, emphasizing the necessity of recomputing original observations rather than relying solely on datum shifts. Tools such as NGS’s HTDP and NCAT utilities facilitate these transformations.<br /><br />Significantly, it notes the deprecation of the U.S. survey foot as of January 1, 2023, urging users to adopt International Feet and strong metadata practices including specifying epochs and units. Best practices for preparing for the 2025-2028 transition include understanding impacts, following NGS updates, and ensuring accurate metadata to maintain geospatial integrity. The key message urges surveyors and geospatial professionals to embrace these modernized geodetic frameworks for improved accuracy and consistency in positioning and heights.

Keywords

NAD83

NAVD88

geodetic datums

NATRF2022

NAPGD2022

GEOID2022

ITRF2020

tectonic plate velocities

U.S. survey foot deprecation

geospatial metadata