I have to compare aerial photographies with geomagnetic data. The photos are georeferenced scanned slides showing structures on the surface. The magnetic data have a certain unit, but the photos do not. For a comparision I need a unit for the structures in the photos (like Delta E colour difference). I vectorized the structures of interest. Now I would like to use some kind of function to calculate the colour difference between a structure within the polygon and the surrounding soil.

Does anyone know such a function in QGIS?

I thought about converting the photos into greyscale images first, to compare the greyscale cell-values. But it would be much better to use the color images.

  • Please decide which of the three desktop GIS products it is that you are using to try and do this because asking the same thing for three or more products violates the "one question per question" of the Tour. If you have no luck with the first then you can always research/ask about another separately. – PolyGeo Oct 15 '16 at 1:26

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