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I am having a DTM and DSM files .I want to develope a Canopy Height Model in Qgis is it possible?

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is it more complicated than subtracting DTM from DSM? –  SS_Rebelious Jul 11 '13 at 14:23
    
how to do that could you eloborate please i am a learner? –  Arun Jul 11 '13 at 15:55
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2 Answers

up vote 2 down vote accepted

Within the raster calculator plugin you would subtract one file from the other. DTM - DSM. This will give you a new file that would be just the canopy.

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The canopy model in Qgis is obtained by subracting DTM from DSM which gives the height of the tree (Kim et al., 2010) thanks SS_Rebelious and Ryan Garnett and i think Ryan Garnett has made little mistake it is (DSM-DTM) and not (DTM-DSM).

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It really depends on you naming of the surface model. I have seen people use DSM and DTM interchangeably. The process is subtract two tasters, the bare earth model from the raster that had the canopy. This will give you just the canopy. –  Ryan Garnett Jul 12 '13 at 13:49
    
ya but when we subract DSM from DTM it gives negative values particularly the height what is the meaning for that? –  Arun Jul 13 '13 at 4:24
    
Then switch the order of the input rasters –  Ryan Garnett Jul 13 '13 at 14:46
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