Geodetic datum

A reference framework that defines Earth’s origin, orientation, scale, and shape so geographic positions and elevations can be expressed consistently.

Coordinate reference system: A system that defines how coordinates relate to locations on Earth or in space. A geodetic datum supplies the Earth reference used by many coordinate reference systems.
Geodetic control network: A network of surveyed points whose coordinates realize a geodetic reference system. Its measured points anchor the datum to locations on Earth.
Horizontal datum: A geodetic reference defining the Earth model and frame used for horizontal positions. It focuses on latitude and longitude rather than elevation.
World Geodetic System 1984: A global geodetic reference system used by GPS and many geographic data products. It is the widely encountered global reference behind many satellite-derived coordinates.
Geodetic coordinate system: A system that locates points using latitude, longitude, and height relative to a reference ellipsoid. It expresses positions using the ellipsoid and orientation established by a datum.
Global Navigation Satellite System: A satellite-based system that provides positioning, navigation, and timing worldwide. Satellite measurements realize modern global datums and connect local positions to them.
Vertical datum: A reference surface or system defining elevations and depths. It governs height values, which need not use the horizontal datum’s reference surface.
North American Datum of 1983: A geodetic datum used for mapping and surveying in North America, aligned with a continental reference frame. It shows how a region’s mapping coordinates are tied to a defined datum.
Reference ellipsoid: A mathematically defined ellipsoid used to approximate Earth’s size and shape. Its dimensions define the datum’s geometric model of Earth.
Coordinate transformation: A mathematical operation that converts coordinates between reference systems. It translates positions between datums whose origins, orientations, or scales differ.

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