[geodesy]
The reference specifications of a measurement system, usually a system of coordinate positions on a surface (a horizontal datum) or heights above or below a surface (a vertical datum).
[remote sensing]
In imagery, the origin and orientation of lines on a surface. Datums are used as part of a coordinate reference system to provide a frame of reference when measuring location on the Earth's surface.
[coordinate systems]
A collection of very accurate control points used for georeferencing map data so that it aligns with the geodetic latitude and longitude coordinate system; a standard position of level that measurements are taken from.
