I'm using QGIS and I'm trying to calculate slope < 20% from a file I have but when I use the raster calculation SLOPE < 20 the result is all black. What am I doing wrong? The data is already in percent.
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1Check the output raster properties and see what its range is. Check the min/max and scaling. Check the histogram to see if has 1s and 0s.– SpacedmanCommented Nov 21, 2015 at 14:03
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1 Answer
The result is all black because all values are 1. To get the true values you have to do (with the raster calculator nomenclature):
("SLOPE@1" < 20) * "SLOPE@1"
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That will give you zero where the slope is greater than 20, and also zero where the slope is zero. I'm not sure that's what's wanted... Commented Nov 21, 2015 at 17:26