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Is it possible to digitize RGB TIFF by color?

I need to select all the vegetation cover types from the image below, which is a part of an aerial photography of an island (http://george.wildlifeintel.com/stitches/southplazaall908geo/doc.kml) enter image description here

I thought I can use ArcScan, but it works with binary pictures, and I need to select different colors.

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ArcScan is meant to digitize drawings (typically scanned cadastral maps or the likes). In your case you want to classify an RGB image.

With a true color image, you can use the image classification toolbar . You'll need to draw some sample polygons and use them for training a classifier. You need spatial analyst licence for that, and I would rather use an image analysis software instead of ArcGIS for this kind of work.

Edit : for a quick and dirty result with green vegetation: compute 2*band2 - band1 -band3 n the raster calculator, then set a threshold manually (changing the symbology), reclassify then convert to polygon.

  • Does it work with RGB files? I tried to do Maximum Likelihood Classification with training samples, but in the end I get just one polygon which covers the whole area. Do you know what the problem might be? How the raster file should be processed before using image classification toolbar? Thank you! – Liza Sep 18 '14 at 18:24
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    As I said, ArcGIS is not thebest software for that. But it should work. see blogs.esri.com/esri/arcgis/2010/08/09/… oradditionnal details. With maximum likelihood, you should take something like 60 pixels per training sample, and make sure that you have one training samle for each "color" that you see (don't put the red and the green vegetation in the same sample. – radouxju Sep 18 '14 at 18:34

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