How to edit a georeference

A georeference stores the relation between rows and columns of a raster map (row,col) and real world coordinates (X,Y) or (X,Y,Z). A georeference is needed for raster maps. A georeference uses a coordinate system.

There are basically five types of georeferences:

georeference corners: a North-oriented georeference to be used during rasterization of vector data or as the North-oriented georeference to which you want to resample maps;
georeference tiepoints: a non-North-oriented georeference to add coordinates to a satellite image or to a scanned photograph, a scanned map, etc. without using a DTM;
georeference direct linear: to add coordinates to a scanned photograph while using a DTM;
georeference orthophoto: to add coordinates to a scanned photograph while using a DTM and camera parameters;
georeference 3D: to create a three dimensional view of maps.

Other types of georeferences (non-editable) are obtained when performing an operation on raster maps:

georeference factor: created by the Aggregate map and the Densify operation;
georeference mirrorrotate: created by the MirrorRotate operation;
georeference submap: created by the Sub-map of raster map and the Glue raster maps operation.

Further, you can have georeference None for raster maps without a georeference (not advised).

Tips:

You can see the type of a georeference by viewing the properties of a georeference.
To be able to calculate with raster maps, it is advised that raster maps of the same area use the same georeference corners or the same georeference tiepoints.
To have a raster map use another georeference than its current one, perform the Resample operation.

To edit a georeference:

double-click a georeference in the Catalog, or
click a georeference in the Catalog with the right mouse button, and choose Open from the context-sensitive menu,
open the Edit menu in the Main window, choose Edit Object and select any georeference, or
in the Operation-tree or the Operation-list, double-click the Edit item, and select any georeference, or
drag any georeference from the Catalog to the Edit item in the Operation-tree or the Operation-list, or
when a raster map is displayed in a map window, you can also choose the Georeference command on the Edit menu in the map window.

Depending on the type of the georeference you selected (or on the type of the georeference of the raster map in the map window), a dialog box will appear or an appropriate editor will be opened:

for a georef corners: the Edit Georeference Corners dialog box will appear;
for a georef tiepoints, a georef direct linear, or a georef orthophoto: the Tiepoint editor will be opened. When editing a georef orthophoto, the Locate Fiducial Marks dialog box will appear first;
for a georef 3D: the Display Options - 3D Grid dialog box appears, in which you can specifying how the 3D view should be displayed in the map window. When the 3D view is displayed in a map window, you can select the Georeference command from the Edit menu of the map window to edit the georeference 3D. The Georeference 3D editor is started with the Georeference 3D editor : Edit dialog box.