The adopted reference system for Europe is known as the European Terrestrial Reference System, 1989 (ETRS89). Coordinates in ETRS89 are expressed as three-dimensional (X, Y, Z) Cartesian coordinates as three-dimensional ellipsoidal coordinates (Φ, λ and H, ellipsoidal height), based on the GRS80 ellipsoid. ETRS89 is mandatory for data exchange under the INSPIRE directive within the EU member states.