The World Geodetic System (WGS) is a global reference framework that defines the coordinate system, reference ellipsoid, and geoid model used by GPS and widely adopted as the international standard for global positioning and navigation applications. The current version, WGS84, provides the fundamental geodetic infrastructure upon which virtually all GNSS positioning is based.

WGS84 was established in 1984 and has been refined through multiple realizations to incorporate improved measurements and maintain alignment with the International Terrestrial Reference Frame (ITRF). The system defines an Earth-centered, Earth-fixed reference frame with its origin at Earth’s center of mass, Z-axis aligned with the conventional terrestrial pole, and X-axis directed toward the intersection of the equator and prime meridian. This geocentric approach is essential for satellite navigation, where all constellation satellites orbit around Earth’s center of mass.

The WGS84 reference ellipsoid provides the mathematical surface for coordinate calculations. Its parameters, semi-major axis of 6,378,137 meters and flattening of 1/298.257223563, closely match the GRS80 ellipsoid used by regional datums like NAD83. This near-identity simplifies coordinate transformations between WGS84 and GRS80-based systems, though small systematic differences exist due to different datum realizations and tectonic motion effects.

For GNSS users, WGS84 is the native reference system for GPS coordinates, when a GPS receiver reports latitude, longitude, and altitude, these values are inherently expressed in WGS84. Other GNSS constellations use related but distinct reference systems (PZ-90 for GLONASS, GTRF for Galileo, CGCS2000 for BeiDou) that are maintained compatible with WGS84 at the centimeter level. Applications requiring coordinates in regional datums must apply appropriate transformations from WGS84, using established transformation parameters or software capabilities to ensure consistency between GNSS-derived positions and local coordinate systems.