[GRASS-user] color anomalies after orthorectification

Markus Metz markus.metz.giswork at gmail.com
Thu Feb 20 23:05:06 PST 2014

On Fri, Feb 21, 2014 at 12:26 AM, Stefan Kiefer <st_kiefer at web.de> wrote:
> 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).

This should only happen with method=cubic or method=cubic_f. The other
resampling methods nearest,bilinear,bilinear_f should not produce
these resampling overshoots.

Markus M

> 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
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