Spatial Reference Frame
A spatial reference frame specifies a spatial coordinate system by combining an abstract coordinate system with an object reference model.
An abstract coordinate system may be combined with many different object reference models. Thus, a geodetic coordinate tied to the Earth object reference model WGS_1984 does not identify the same place as when tied to the Earth object reference model EUROPEAN_1950, or when tied to an object reference model for Mars.
A spatial reference frame specification includes:
- Object Reference Model (ORM) -- A geometric description (model) of a reference object embedded in (and serving to orient) that frame. An Earth Reference Model (ERM) is a special case of an ORM.
- An Abstract Coordinate System (CS) specifying how a tuple of values uniquely determine a location with respect to the origin of that frame. By extension, that tuple also specifies a location with respect to the reference object.
- (optionally) a valid region description or specification to limit the region of applicability.