Re: [GRASS-user] Joining Two Adjacent Raster DEMs

Sat, 17 Mar 2012 07:44:03 -0700

On 03/17/2012 01:57 AM, Rich Shepard wrote:
  Two source DEMs each cover half the project analytical area. I want to
join the two into a single raster DEM. Tried using 'r.mapcalc dem_proj =
dem2 + dem3' but that did not produce anything visible. From reading

I think that the '+'operator honors NULL cells, so anywhere that is NULL in either raster will be null in the result. That's not what you want in this case.

mapcalc.pdf and mapcalc-algebra.pdf I know the module is designed for
combining multiple raster maps cell-by-cell. I've not found how to
edge-match and join two rasters that do not have overlapping coverage.

  Please pass me a pointer to the appropriate module to use for this
operation.


r.patch does this.
As per the man page, be sure to set the region to *all* input rasters in advance:
g.region rast=dem2,dem3

TIA,

Rich

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-- 
Micha Silver
GIS Consultant, Arava Development Co.
http://www.surfaces.co.il


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