Hello, I hope I can get some help here. I am using the stereo images produced by the European Space Agency probe, Mars Express, currently orbiting around Mars. ESA produce their own 3d data, with a 'Nadir' image draped over the top (they claim not to use ENVI, though, although they do have a support license). The ENVI module claims it needs 'RPC files' (Rational Polynomial Coefficient) to describe the camera model before DEM extraction can take place. ESA support have yet to supply me with these files. Is it possible to construct them from camera documentation, or in some other way ? Regards DJBarney