[GRASS-user] i.topo.corr ignores pixel at the edge of the computational region

[Markus Neteler]

On Fri, Dec 4, 2015 at 4:37 PM, Panagiotis Mavrogiorgos
<pmav99 at gmail.com> wrote:
> On Fri, Dec 4, 2015 at 4:34 PM, Panagiotis Mavrogiorgos <pmav99 at gmail.com>
> wrote:
>>
>> Hi all,
>>
>> Why is i.topo.corr ignoring/throwing away some pixel rows at the edge of
>> the computational region? It is not a big deal but am I doing something
>> wrong?
>>
>> In the following image the purple is the illumination model while the
>> brown area is the elevation model at the upper right corner of the
>> computational region
>
>
> OK, I think that I figured it out. I think that the problem is that the dem
> has different resolution than the satellite imagery (i.e. 10m vs 30m).
>
> Question. Is the output we get from a higher resolution dem usable, or
> should we resample it?

For i.topo.corr I would recommend to resample the DEM to the
resolution and pixel position of the satellite image.

g.region raster=dem align=image -p

then
https://grasswiki.osgeo.org/wiki/Interpolation#Resampling_of_raster_maps_to_coarser_resolution
--> r.resamp.stats -w ... method=bilinear ...

now
i.topo.corr ...

HTH,

Markus