[GRASS-user] Re: i.atcorr negative DEM

[Elena Mezzini]

2011/5/24 Markus Neteler <neteler at osgeo.org>

> On Tue, May 17, 2011 at 10:57 PM, Elena Mezzini <elena.mezzini at gmail.com>
> wrote:
> > Elena Mezzini wrote:
> >> Markus Metz-2 wrote:
> >>>
> >>> On Tue, May 17, 2011 at 10:08 PM, Elena Mezzini
> >>> &lt;elena.mezzini at gmail.com&gt; wrote:
> >>>>
> >>>> On Tue, May 17, 2011 at 9:22 PM, Elena Mezzini
> >>>> &lt;elena.mezzini at gmail.com&gt; wrote:
> >>>>> Hi all,
> >>>>> I'm once again in trouble with i.atcorr in GRASS6.5.svn.
> >>>>> I notice that my output reflectance images are strange: there are
> some
> >>>>> areas
> >>>>> that are really bright and other that are really dark. Both seem to
> >>>>> match
> >>>>> with my DEM raster.
> >>>>> Could there be problems with negative values in DEM?? I'm in a
> coastal
> >>>>> area
> >>>>> and there are some real altitude negative values.
> ...
> ...
> >> g.region rast=dem_sross_srtm
> >> r.mapcalc "dem_sross_srtm_pos = if(dem_sross_srtm < 0, 0,
> dem_sross_srtm)"
> ...
> > No differences between negative and positive values...
>
> What do you mean precisely?
>
> I mean that i.atcorr automatically considers negative values equal to 0. So
the results of i.atcorr with negative values or with negative values made
equal to zero are the same.
So I still have problem with all the bands of landsat probably due to DEM.

Elena
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