[GRASS-user] patching dems together

Markus Metz markus.metz.giswork at googlemail.com
Thu Jul 9 13:58:14 EDT 2009

stephen sefick wrote:
> values range from ~-9 to ~800 there is a tile which has no elevation.
> The patched dem only ranges from 0-296.  This may be the problem.
It seems that the current computational region did not include all tiles.
Try setting the computational region to include all tiles with g.region
rast=<all your tiles>.
Check the resolution of each tile with r.info -s. If they are not all
the same, use the coarsest resolution to be safe.
Check the resolution of the computational region. It must be the same
like the coarsest resolution, if not, set it to that.
Set the same color rules for all tiles. Use srtm or etopo2 but not
elevation because elevation will be different for each tile.
Display all tiles, zoom to the computational region.
Patch all tiles.
Set the same color rules to the patched DEM like to the tiles.
Add the patched DEM to the display, it should look like the previous
display with all the tiles.

Good luck,

Markus M

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