[GRASS-user] DEM Import - lost elevation data

Hamish hamish_nospam at yahoo.com
Mon Aug 27 04:55:42 EDT 2007

Richard Chirgwin wrote:
> I have imported models from srtm.csi.cgiar.org, using ASCII downloads. 
> To import the models, I'm using r.in.gdal.
> If I import the model to a new location, everything looks fine, and if I 
> query the imported map, I get results that make sense. For eg:
> r.what -f input=testdem at PERMANENT east_north=151.3524554,-30.85835173
> returns:
> 151.3524554 -30.85835173 1026
> (I have taken out the | delimiters to make it more legible)
> But if I then import a different DEM tile from the same site, in the 
> same format, and load it into the same location, it loads without the 
> elevation. Hence:
> r.what -f input=DEM2 at PERMANENT east_north=119.2521986,-30.56112713
> returns results like:
> 119.2521986 -30.56112713 *
> If I load the second DEM into a new location, it will work fine but no 
> other DEMs will show their elevation data.
> Can anyone provide suggestions as to the likely cause?

"*" as a value indicates that the value of that cell is NULL. One
possible/ probable reason for that is if the map is outside of the
current region. Anything off the end of the map will be reported as NULL.

That's the raw value of the data, nothing to do with color settings,
those are applied later.

try  "g.region -p rast=DEM2" to set the current region to the map's
extents. Also,
  g.region -p rast=DEM1,DEM2
will zoom to a region which covers both maps.


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