gvSIG-Desktop 1.1. Manual de usuario.

Changing a layer’s reference system requires a conversion or transformation operation, or a conversion and transformation operation:

• A coordinate conversion operation is applied when the layer’s CRS datum coincides with the view’s CRS datum. In other words, both CRSs correspond to the same geodesic reference system but use different coordinate systems.

In this case, the “No transformation” option would be selected.

• A coordinate transformation operation is applied when the layer’s CRS datum does not coincide with the view’s CRS datum. In this case, two types of coordinate operations can be carried out:
  • The operation may only involve a transformation operation. This is the case when the layer’s CRS coordinate system coincides with the view’s CRS coordinate system, that is to say that the position is expressed in the same coordinate system in both CRSs but using different datum.
  • The operation may require a joint transformation and conversion operation because neither the datum nor the coordinate system of the layer’s CRS and the view’s CRS coincide.

If such a transformation operation is required, select the type of transformation in the layer’s CRS’ selection box and click on “Next”. This opens the corresponding transformation panel.

There are three types of transformations: “EPSG transformation”, “Manual transformation” and “Transformation by grid file”.