[GRASSLIST:2690] Re: stitching geotiffs

[Richard Greenwood]

Martin du Saire wrote:

> Hi,
> 
> I am a newbie to GRASS (XT, Cygwin/XFree86; GRASS5.0) and GIS trying to 
> stitch together a set of NLCD Geo-Tiff  (USGS Landsat-5, etc.) data 
> files for a set of contiguous states in the US.  I finally figured out 
> how to import them using r.in.gdal -o.  (If there is some inherent 
> problem with overriding the projection checking, please let me know.)

If you are importing an image in UTM Zone X into a location defined as 
UTM Zone X, then you are doing the correct thing by using -o. (You 
should not use -o to import Zone X into a location of Zone Y). You may 
also want to use -e, which extends the location if needed.

> For starters, how do I go about importing the individual files with 
> their corresponding UTM zone designations into the same project?

Do I understand correctly that you have images in Zone X, Y Z ... and 
want to have them all in a single projection? If I understand correctly, 
then you need to use r.proj to reproject from the individual zones into 
the single target projection. But maybe I do not understand you goal.

> Assuming I can figure that out, do I use r.mask to remove the background 
> from each of these maps?

You probably do not need to mask. I am guessing that the background is 
NULLs?

-- 
Richard Greenwood
www.greenwoodmap.com