[coordinate systems]
Also known by the acronym NAD 83. The horizontal datum and spatial reference system for geometric positioning used in Canada, Greenland, and the United States. NAD 83 uses the Geodetic Reference System 1980 (GRS80) ellipsoid as a reference surface and the Bureau International de l’Heure Terrestrial System of 1984 (BTS-84) for orientation. NAD 83 is defined to remain constant over time for points on the North American tectonic plate.