[GRASS-user] color anomalies after orthorectification

Stefan Kiefer st_kiefer at web.de
Thu Feb 20 16:25:31 PST 2014

OK, I found a workaround.
with r.mapcalc I identify all values lt 1 and gt 254 and set them to 1 
resp. 254. Actually not a nice way but the result is good enough for the 

Anyway, I still would be thankfull for an explanation of the phenomenon, 
moreover a better solution to avoid that behaviour.

best regards


Am 21.02.2014 00:26, schrieb Stefan Kiefer:
> Hi,
> I tried to orthorectify aerial photographs.  That worked fine by now, 
> until i got scans wich appear to be darker as before. At least this is 
> the first observation I made. The effect occured with that scans is, 
> that after rectification some of the dark areas become white (or 
> rather null, querying that cells result in -0.722622310236638).
> Has anyone had similar experiences when rectifying aerial photographs. 
> And hopefully a hint how to avoid this damages. I suspect that the 
> orthorectified images become double precision whereas the imported 
> scans are integer...
> best regards
> Stefan
> _______________________________________________
> grass-user mailing list
> grass-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user

More information about the grass-user mailing list