> Andruit: > > I have several raster maps (aspect, slope, tand_curv etc.). .. > > And then I would like to check Pixel by Pixel > > if slope = steep and aspect = North etc. > > then > > "Value of the checked pixel" + 10 > > > > else > > > > .... > > > > Has anybody done this before? Is it possible to combine several > > raster maps without losing any information?
sure, it is a basic thing for GRASS probably for 20 years. Combining the maps into one first is a totally unnecessary step. Jarosław Jasiewicz wrote: > Thaw what you described has SpatialGridDataFrame in R. Simply you can > import all raster data to one SGDataFrame and you can do there what you > need.... It seems, becouse I can't understand for what you need 1 file > instead of three or for and use mapcalc for that operation. Simply > seems that mapalgebra (r.mapcalc) it is what you realy need e.g. r.mapcalc with the spearfish demo dataset: g.region rast=elevation.dem # GRASS usually measures aspect in degrees CCW from East # logic: if(this is true, then do this, otherwise do this) # "slope", "aspect", and "elevation.dem" are map names. r.mapcalc "test = if(slope > 10 && (aspect >= 45 && aspect < 135), elevation.dem, null())" d.rast aspect d.rast -o test you can also use create a MASK map if the r.mapcalc logic starts to get too confusing, to build up your query bit by bit. see the raster intro page. http://grass.ibiblio.org/grass63/manuals/html63_user/rasterintro.html see also r.mapcalculator for an nice GUI frontend for r.mapcalc. Hamish _______________________________________________ grassuser mailing list grassuser@grass.itc.it http://grass.itc.it/mailman/listinfo/grassuser