Well, if you drag-n-drop either of the images into the viewport in CE, the terrain creation dialog will come up.
Best do this in a new scene, for both image files.
If the propoposed scene coordinate system (SCS) and the extent/offset don't exaclty match for BOTH images, the georeferencing info is wrong.
What you then can do, e.g. if one of the files does not have a proper georef definition or e.g. does not recognize a projection, therefore falls back to metric scene coordinates, use the one that has proper georeferencing data, CREATE the terrain and then edit the texture file in the terrain object. The reason for this is that when you're still in the terrain creation wizard, loading a new map will reset the extent in the wizard. If the terrain is created, loading a new picture will only edit the picture.
But the images MUST MUST MUST depict the same extent, since basically BOTH of the textures are only 'draped' on top of the terrain geometry (scaled to the ends in both dimensions). The georef info is only used to create the terrain geometry, the images are then mapped over this geometry, even if the extents don't match. So be very cautious.
Ok?
Matthias Buehler
Head of 3D Technologies
twitter: @MattB3D
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Garsdale Design Limited
matthias.buehler@garsdaledesign.co.uk
www.garsdaledesign.co.uk