Re: [GRASS-user] Subtraction of raster maps
Hi Thomas, On Wed, 24 Jun 2009 08:42:11 +0200 "Thomas Becker" wrote: > Hi, > > 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" if I understand right this might work for you, if everything that is not a building in your 'buildings' map is no data (null): r.mapcalc "newmap = if(isnull(buildings),landcover,null())" > 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? > > Thanks, > Thomas Regards, Otto ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Subtraction of raster maps
Thomas Becker wrote: > Hi, > > 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" > r.mapcalc "newmap = if (isnull(buildings), landcover, null())" may do the trick, assuming that the buildings map has nodata where there are no buildings. The newmap would have nodata where there are buildings otherwise landcover. Markus M > 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? > > Thanks, > Thomas > ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Subtraction of raster maps
Hi, 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? Thanks, Thomas -- GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT! Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
