gvSIG-Desktop 1.12. User manual

If you wish to export a layer to an Oracle database, you will also be asked if you wish to include the view’s current coordinate system in the table at the end of the process described in the manual. This may be useful in cases where we do not wish to include such information in the table for reasons of compatibility with other applications or information systems.

To work with two Oracle geometries (the most common case is an intersection), the two geometries must have the same coordinate system. Each geometry has an SRID field which can have the value NULL.

For instance, if we have a table with geometries in EPSG:4326 (Oracle code 8307) and another with geometries in EPSG:4230 (Oracle code 8223), it will not be possible to carry out SQL instructions to perform calculations directly between the geometries of one table and another. However, if these tables’ geometries do not have a coordinate system (i.e. SRID is NULL), then operations can be performed between the geometries of these tables, bearing in mind the errors involved in carrying out intersections between different coordinate systems.

When reading a table whose geometries have a coordinate system set at NULL, it is understood that the user will make sure that the geometries are appropriate for the current view, since no reprojection is possible (this may change with the new gvSIG extension for the advanced use of coordinate systems).

In short, not storing the coordinate system allows for a more flexible use of geometries.