World Geodetic System of 1972 (WGS 72)—A set of constants specified by the U.S. Department of Defense in 1972. Replaced by the World Geodetic System of 1984.

World Geodetic System of 1984 (WGS 84)—A reference frame defined by the National Imagery and Mapping Agency (NIMA; now NGA), and used by the U.S. Department of Defense. It was used as a reference frame for broadcasting GPS Ephemerides beginning in 1987. Its origin is at the Earth’s center of mass, and its third axis is positioned by the Conventional Terrestrial Pole. The defining parameters for its ellipsoid are the semi-major axis (a) and flattening (f). See also WGS 84 (730); WGS 84 (873).

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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