I am trying to georeference sovet military maps from maps.vlasenko.net. I have manage with one, but to my surprise I am failing badly with georeferencing a second file (M33-3 map). Let me go piece by piece.

I am using georeferencer plugin of QGIS. I have defined about 20 ground control points, and below I paste my settings: [image file below]

Now the problem when "targer resolution" tickbox is checked I am getting "failed to compute GCP transform: transform is not solvable". I am surprised to find that the parameters describing the resolution of the output file should determine whether the GCP problem can be solved on not.

When I set the resolution to 1 -1 i get an output file which is (2x3 pixels - TWO by THREE pixels, six in total, any other resolution results in the above error).


  • why the vertical resolution is negative? Setting it to a positive value is not possible (program does not accept any string which does not start with a minus sign)
    edit: now, due to comments, I know that the resolution referes to "distance" between the two pixels in the real world but what is the exact definition? distance in "degrees" between two pixels meaning if I set resolution to -0.001 I will get 1000 points between 48N and 47N?

  • The output file if it is generated is 4416x2868, while the inupt file was 3640x3690. How do I prevent QGis from redusing the vertical resolution?

These are my points:


enter image description here

  • is the photo I enclosed visible? I see it in the source, but I do not see it on stackexchange. – Lacek Jun 10 '16 at 18:52
  • 2
    Vertical resolution is negative because rows of the image are counted from top to bottom but north coordinate is growing from the equator towards the north pole. I suppose that pixelx and pixely are counted towards right and bottom from the top-left pixel of the image but I am not sure. – user30184 Jun 10 '16 at 18:55
  • Ok, so what then the "per inch" mean in this context? Does it refer to map "paper" size or real world size? Does that mean that instead of 1,-1 I should be using resolution of say 3000 dots per 200 km which is a very tiny number on the dpi. – Lacek Jun 10 '16 at 18:58
  • setting resolution to 0.00001 results if extrelemy long computation time, and I cannot set the resolution any lower (program does not allow it). the "up" and "down" arrow change the resolution by 1, so I guess the values expected are of the order of unity.... – Lacek Jun 10 '16 at 19:05
  • I have checked that by setting the resolution 0.001 by say 0.0007 I can get a "squarish" map. But what exactly these values 0.001 and 0.0007 mean? Decreasing these values seems to increase the file, so this is not a "resolution" of a file meaning number of pixels, but physical distance between the two pixels.It would seem that 0.001 means "1 pixel equal to about 100m", but what is the exact definition? – Lacek Jun 10 '16 at 19:25

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