CRS - Coordinate Reference System

A CRS is a coordinate system that can be used to geo-reference a particular place on earth.

The most common CRS is the geographic coordinate system also known as LatLon, which specifies a point on earth by a two angles, the geographic latitude (height) and longitude (width).

Since the earth is no sphere, it needs to be approximated by an ellipsoid. For LatLon coordinates the ellipsoid being used is the so called WGS84 datum.

Other common CRS include

  • Mercator
  • UTM (Universal Transverse Mercator)
  • ECEF (Earth Centered Earth Fixed)

For a more complete list see here.