I assumed you had a tape with nothing but DEM data, like an pure
image file, not some "crazy" format - ie the DEM format from
USGS. If the tape contains non-dem data, ie record lengths,
offsets, row and column info, etc, then using dd isn't so
straightforward. I think someone needs to rewrite the extract
programs to NOT depend on 9-track tape - ie to work from
/dev/mt0, /dev/rst0, a file, anything. Any takers?