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The Earth and Its Coordinate System
Published in Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard, Thematic Cartography and Geovisualization, 2022
Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard
Taking advantage of GNSS and other observational and measurement technology, the NGS plans to modernize NAD83 and NAVD88 as part of the National Spatial Reference System (NSRS). The NSRS, the fundamental spatial reference system for the United States, ties together two ideas: geometric datum and geopotential datum. A geometric datum (or terrestrial reference frame) provides information about latitude, longitude, ellipsoid heights, and crustal velocities. Ellipsoid height is the perpendicular distance from the reference ellipsoid surface to Earth's surface. An ellipsoid height can be determined via GNSS signal information. Crustal velocities report the speed at which Earth's crustal plates are moving and are important when determining accurate coordinate values. The new geometric datum is called the North American Terrestrial Reference Frame 2022 (NATRF2022). A geopotential datum provides information about the geoid, gravity, and elevations. NAVD88 will be replaced by the North American-Pacific Geopotential Datum (NAPGD2022). Coupled with NAPGD2022 will be a new geoid model (GEOID2022) that provides geoid height (the distance measured along a line perpendicular from the geoid to the reference ellipsoid). In addition, NAPGD2022 will provide orthometric heights (elevations commonly reported on topographic maps).
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The National Geodetic Survey (NGS), an agency of the National Oceanic and Atmospheric Administration, defines and manages the National Spatial Reference System (NSRS). The NSRS is a consistent coordinate system that defines latitude, longitude, height, scale, gravity, and orientation throughout the United States. The accuracy and accessibility of NSRS depends in large and growing measure on use of GPS.
Automated location correction and spot height generation for named summits in the coterminous United States
Published in International Journal of Digital Earth, 2020
Samantha T. Arundel, Gaurav Sinha
Spot heights were compared to elevation values of geodetic control stations maintained by the National Geodetic Survey (https://geodesy.noaa.gov/NGSDataExplorer/). The National Spatial Reference System (NSRS) serves as the United States depository for geodetic data, whose clients are global in reach. The NSRS includes geodetic survey results, tools to manipulate geodetic data, and metadata describing the products. Each geodetic control station maintains either a precise latitude/longitude employed in horizontal control or a precise orthometric height utilized in vertical control, or both. In the Data Explorer, points are classified by control type, which should be considered when evaluating reference values.