What is datum?

Datum refers to a point or a set of coordinates that serve as a reference for measurement or navigation purposes. In geodesy and cartography, a datum is used as a basis for determining relative positions of geographic features on the Earth's surface. It typically consists of a coordinate system that is defined by a specific point or a set of points, as well as a set of parameters that define the orientation and shape of the coordinate system relative to the Earth's surface or a reference ellipsoid. There are many datums in use around the world, each with its own set of parameters and coordinates. Datums are important in many fields, including surveying, mapping, and navigation.