[GRASS-user] aerial photo rectification with coarse elevantion model

[Stefan Kiefer]

Hi,
for orthorectifying aerial photographs I tried using the srtm data. 
Unfortunately the coarse resolution leads to remarkably distortions 
expecially in steep areas. It appears that the photograph is projected 
on the 90x90 m squares of the dem. For a certain area I got a 25 m dem 
this leads to better results, but still mosaiked to the dem resolution. 
I tried to resample the dem with a resolution of 1m (which is the 
resolution of the aerial photographs). First this attempt didn't succeed 
with r.resample neither with r.resample.rst. Finally I managed it 
(actually I don't know anymore, I believe it was by mapcalculating the 
dem multiplying by 1 and a region resolution of 1m and resample(rst) it 
afterwards).
Whatsoever it didn't help. Has anyone an idea how to interpolate a dem 
with a finer resolution? or how I can orthorectify the photographs 
without the mentioned distortions. I can live with a slight error in 
steep areas, but I need a continuous photograph.

thanks for your consideration, best regards and a merry christmas

Stefan