Modernizing the Datums of the National Spatial Reference System

Abstract

AbstractThe National Spatial Reference System (NSRS) is the official coordinate system for all geospatial activities performed by civilian federal agencies of the United States, including National Oceanic and Atmospheric Administration's navigational charts. Two of the datums that make up the bulk of the NSRS, the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88), were created with the most accurate surveying technology available in the 1970s and 1980s. However, analysis over the last decade has proven that both datums contain systematic errors at the few meters level. While there have been improvements to these datums over the years, they have all been restricted to adjusting subsets of coordinates within the datum, rather than replacing the datum itself. However, the rise of near-real-time positioning technologies at the few centimeter level has made it no longer viable to maintain the two datums.The National Geodetic Survey is engaged in a decade-long effort to prepare the NSRS user community and collect the necessary data to define two new datums that will not only replace NAD 83 and NAVD 88 but also reduce the overall reliance of those two datums on passive control. The two new datums are expected to be completed and jointly released in 2022.