raster overlay

Sue Tewalt x6437 stewalt at ncrds.er.usgs.gov
Thu Dec 5 09:05:47 EST 1996

Perhaps Alberto is only trying to lay the rasters side by side and not
manipulate the actual category values. In  this case,
r.patch the rasters in the proper order would get him what he desires. 
> Alberto:
> The colors will change when adding layers together using r.mapclac.  This
> is because the values of each layer are added together (where they overlay)
> and this results in new & different values.  You are overlaying correctly.
> Pat Luther
> At 10:27 AM 12/3/96 +0000, you wrote:
> >Hello
> >  I'd like to know how can I create a raster file by an overlay 
> >between some other. I tried using r.mapcalc with "+" but the result had
> >changed colors. 
> >Thanks for help
> >Alberto Giorgi
> >

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