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I am currently attempting to orthorectify an image using GDAL. I have a very detailed DEM that I would like to rectify the image on top of. However, the DEM is smaller than the image itself; this is fine though since I only want to orthorectify a small portion of the image. However, to do so I must crop the image to that small region or orthorectify and then crop. The issue is that since the DEM is smaller than the image, orthorectification failed with the "too many points failed to transform" error message with GDAL warp. As such, the alternative would be to crop the image, but I have no idea how to crop non-orthoimages in GDAL. The input file is currently in a VRT file which refers to the originalDEM file and contains the RPC camera information.

So in short, how can I accomplish this task with GDAL? Are there any other tools I can use? Or will I have to completely rethink my approach? Is there a way I can buffer my DEM with 0 values so that it orthorectifies without errors and then crop it? Or would I have to figure out how to crop it first?

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I would try to add a low resolution DEM (e.g. SRTM 30m) to fill the gaps where your high resolution DEM is not available. The problem with a crop before orthorectification is that the RPC link image coordinates with ground, so if your image is not georeferenced and you crop it, this relationship will be detroyed.

  • How would I do this while having the high resolution DEM take priority? – Skylion Jul 12 '16 at 14:07
  • It turns out that as long as the high resolution images are list on the command line arguments for gdalbuildvrt, they will take priority. So all I had to do is list a low-resolution model for filler. Thx for the help! – Skylion Jul 12 '16 at 15:45

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