Its awful! That does work (in tsch so far! I tried -not alone- for hours... Thank you very much, Nikos! Maybe you know a way to make r.mapcalc "quiet"? Or maybe to query a rastermap col-row wise? Greetings from Potsdam at the moment. achim Nikos Alexandris schrieb: > Try this: > r.mapcalc river="if(river==$old, $new, null())" > > Cheers, Nikos > >