Coordinate Reference System (CRS)
A combination of at least one coordinate system together
with its spatial datum. In a CRS,
positions or locations of geographic information are described by coordinates.
spatial positions are described by coordinates
in a coordinate reference system -
coordinate reference systems of geodata
have to be homogenized when
different geodata sets are combined
[Voser
1996, Voser 1998, Voser
2007, p.7]