[GRASS-user] DEM Import - lost elevation data

[Richard Chirgwin]

Greetings all,

I think there's something I don't know about how Digital Elevation 
Models work.

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?

Richard Chirgwin