[GRASSLIST:508] DEM Generation from stereo optical imagery

[Gerald Buckmaster]

Greetings,

I am looking for a low cost DEM generation solution.  I've seen several 
commercial software packages like Orthoengine, Orthobase, AsterDEM, etc. that 
can generate DEM/DTM from stereo imagery, but nothing in the open source.  
Can GRASS be utilized to generate DEM?  If so, what commands/scripts will do 
so, and how labor-extensive is the process?  If not, can anyone describe, in 
layman's terms, what is required to create software that can generate DEM 
from stereo imagery?  I am specifically targeting ASTER 3N and 3B 15m stereo 
image set as the input data.

TIA

Gerald Buckmaster