X.B.4.2 Global coordinate systems

Global coordinate systems correspond to CoordSys objects. However one makes the distinction between:

1.

The basic coordinate system identified with integer 0.

2.

Coordinate systems which have a correspondence in the DataBase from which they have been or may be extracted. Those coordinate systems are identified with an integer larger than 0.

3.

Other user defined coordinate systems which have no correspondence in the DataBase. They are identified with integer -2000.

Not that the user is responsible for the use he makes on coordinate systems defined in DataBase. In particular, it is true when several DataBases are used.