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Again a Grass 7 question. I have the output of a modelling run as matlab file, which I can export as tiff and load as geotiff. OK - now can I extract the data/convert this tiff into a raster proper? I also have ArcGIS 9.3, should this be the better way (I think this would work with the raster calculator - In ArcGIS 9.3, how do I split a 3-band raster (.tiff) file and summarize the band values?, but I do not have ArcGIS at the moment to try this). Still curious if Grass 7 would be able to do this.

Additional info: The data contain calculated wind speeds, but the display is as color band 0-255. So the question is how to retrieve the winds speeds? I can only see them in Matlab, but in order to correlate and spacially reference I have to export the result - as tiff...

Thanks in advance, Peter

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2 Answers

You should not export the wind map as RGB GeoTIFF but rather as Floating point GeoTIFF.

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what is a raster proper ?

When you import a multiband raster in GRASS GIS, it is automatically splitted in these 3 color bands

The command:

r.in.gdal -o input="test.tif" output="test"

gives you 3 raster test.red, test.green and test.blue and each can be summarised.

If you want to combine these red, green and blue raster maps into a single map:

r.composite red="test.red" green="test.green" blue="test.blue" output="test"
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Gene, thank you! My question was too imprecise. The data contain calculated wind speeds, but the display is as color band 0-255. So the question is how to retrieve the winds speeds? I can only see them in Matlab, but in order to correlate and spacially reference I have to export the result - as tiff... –  Peter Apr 6 '13 at 17:34
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You can see them because matlab transforms the byte data(which it has a range of 0-255) to actual data for each cell. figure out how transformation works, and apply the same routine. –  nickves Apr 7 '13 at 1:31
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