Hi Andre, On raster algebra, operations using null will return null while operations with 0 behaves like expected. Ex: 12 x null = null 12 x 0 = 0
Null is interesting to use on areas you don't have / want to represent, like an ocean... Hope it helps Daniel On Feb 5, 2012 12:03 AM, "ALT SHN" <i.geograf...@alt-shn.org> wrote: > Hello, > > I have a technichal doubt. I used* v.to.rast.constant *to tranform a line > vector layer to raster. This meant i have a raster with NULL values. > The output raster is to be used in map algebra operations. > > So my question is: Is it advisable to set the Null cells to 0? I know > r.calc works with NULL values, and I know that NULL is not the same as 0, > however I never understood what difference does it make if any. Considering > these two scenarios what do I win and what do I loose? > > Any enlightening will be very aprecciated! > > Thanks, > > André Mano > --------------------------------------------------------------- > Associação Leonel Trindade > SOCIEDADE DE HISTÓRIA NATURAL > > Apartado 25 2564-909 Torres Vedras Portugal > Sede e Biblioteca: rua Cavaleiros da Espora Dourada, 27A 2560 Torres Vedras > > Laboratório de Paleontologia e Paleoecologia: Polígono Industrial do Alto > do Ameal 2565-641 Ramalhal > http://alt-shn.blogspot.com > www.alt-shn.org > > _______________________________________________ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user > >
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