In order for the x, y, and z coordinate values to have real world meaning, spatial referencing must be provided, including the coordinate system, the geodetic reference system, etc. The coordinate system refers to the horizontal projection being applied (e.g. UTM, Lambert Conformal, or Latitude and Longitude) and the definition of the vertical values (e.g. meters or feet, referenced either to some vertical datum or the centre of the earth). The geodetic reference system defines the choice of horizontal and vertical datums, etc. Objects carrying such information are said to belong to the class SpatialReferencing.