determining error of DEM

[Rado Bonk]

Hi GRASSusers,
I need to examine the DEM error, before using the DEM for future
analysis.
I have a big 140x 80km,20mx20m resolution elevation grid from vertically
highly exaggerated montain area. Vertical exaggeration is almost
5000m, and slope angles go up-to 85-90 degrees. The grid was computed from
stereo pair of two satellite images, and control points from ground
photogrammetry were used to decrease the error in DEM.
Using just visual control in nviz2.2 I have found that, on same places are
smooth-like areas (very smooth surfaces) among the typical terrain
features. Since accuracy of the whole DEM is good enough (elevation error
is less than 10m) I would like just to examine these local errors in DEM.
Any ideas?

Thanks,

Rado

Rado Bonk
Geography and Geology
UNO, Nebraska, 68182-0199,
rado at cosmos.unomaha.edu