Hi All, So I have got a problem similar to Anneley. I have a Radarsat image collected in SAR FINE 4F, PATH IMAGE nominal resolution 6.25m. I used the method suggested in the Link ID 2236 to georeference the beta nought image. I would now like to convert the beta nought to sigma nought. As I understand it you need the beta nought to perform the conversion, see this link www.space.gc.ca/asc/pdf/tn5001r4.pdf e.g. beta nought -> conversion to -> sigma nought Once again though I run into the problem that the georeferenced beta nought image is not in the native radarsat format. I have tried to run the conversion on the raw Radarsat data but am then asked for a DEM. I have a DEM of the area (clipped and masked to match the Radar data) but the dims dont match with the unreferenced raw radarsat data. I am a little confused, how am I supposed to use a georeferenced DEM in a procedure that will only accept an unreferenced image? This seems counter intuitive? I have considered reading the clipped DEM into IDL removing all zero values using an ROI then writing the result to an unreferenced image file using the dims from the raw radar data. Is this a viable solution to my problem or am I missing something? If so could someone point me towards some code or examples to help. I have written some IDL batch files but nothing too advanced and would like to solve this matter as soon as possible. Kind regards and many thanks for your help and suggestions, Wesley