[GRASS-user] i.topo.corr bug in GRASS 7.0.3?

[Markus Neteler]

On Tue, Oct 18, 2016 at 12:24 PM, Stefan Sylla <stefansylla at gmx.de> wrote:
> I have two Lansat 8 scenes from the same path/row and I try to perform
> topographic correction with i.topo.corr. I have converted all images to
> reflectance (DOS1) using i.landsat.toar. After that I tried to correct
> topography using i.topo.corr.
>
> It seems to work fine with the 1st scene, but I get strange results with the
> 2nd scene:
>
> Range of Scene 1 (Band 5) before i.topo.corr:  min = 0.133723349810153  max
> = 0.906354180100938
> Range of Scene 1 (Band 5) after i.topo.corr: min = 0.133760732072622  max =
> 0.907846862031268
> Seems fine.
>
> Range of Scene 2 (Band 5) before i.topo.corr: min = 0  max =
> 0.832036359894079
> Range of Scene 2 (Band 5) after i.topo.corr: min = -17160.1716925017  max =
> 1438.29470705194
>
> Don't understand why the value-range in scene 2 completely changes after
> i.topo.corr.

I assume that both scenes overlap like 100%?
Is it a rugged terrain? And: which method did you use?
Note that the cosine method saturates when the slope is > 40° if I
recall correctly.

Markus