[GRASS-user] Subtraction of raster maps

Thomas Becker thomasGeo at gmx.de
Wed Jun 24 02:42:11 EDT 2009


I know it is pretty standard to subtract to maps from each other and I do have the command for r.mapcalc, but it is not doing what I expect.

I have a landcover map and a map wit buildings. Both are raster maps. Now I want to get rid of the areas in the landcover map that are covered by buildings. To get this done I wrote:

r.mapcalc "newmap = landcover - buildings"

The outcome is a map showing only the buildings and no landcover. It also doesn't matter if I change the order in the equation, the result is the same: Only buildings are delivered.

Can you help me out with this?

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