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It seems pretty simple but until now I could not find a proper solution: In a given raster i want to know the number or ratio of e.g. red pixels.

Edit: to be more precise: I have a number a arial photos and want to estimate vegetation cover, so I tried to estimate/count the number or amount of green pixels. If there is an other solution to estimate vegetation cover, i am open to any other way.

First Attemps were raster statistics and inspecting histogramms, but the results were not clear to me.

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  • ArcGis 10.1 or Qgis 2.2
    – user16032
    Commented Mar 2, 2014 at 20:49
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    Thank you for your comment, @Aaron. Would you mind re-posting it as an answer?
    – whuber
    Commented Mar 3, 2014 at 15:33

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One of the most basic methods of estimating vegetation cover is to first calculate NDVI (assuming you have a near infrared band and a red band in your imagery). The formula is:

(nIR-red)/(nIR+red)

Then threshold the image by creating a binary raster dataset, usually via the Reclassify or Con tool. Once you have a binary raster dataset, simply calculate the number of 1's vs 0's.

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  • Thanks for your help, but I have only RGB channels, this is the reason why i want to use only the colour.
    – user16032
    Commented Mar 4, 2014 at 19:48
  • If you are in the USA, you can download 4-band imagery for large portions of the US. See Earth Explorer.
    – Aaron ♦
    Commented Mar 4, 2014 at 19:57

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