[GRASS-dev] compile 6S library in GRASS

[Markus Metz]

On Thu, Jun 28, 2018 at 2:23 PM, Stefan Blumentrath <
Stefan.Blumentrath at nina.no> wrote:
>
> Thanks for clarification, Markus.
>
>
>
> So, what would a module that puts together an 6s input file (which is
what Roberta is about to produce if I understood correctly) have to do with
a visibility map then? Nothing, probably?

feed the visibility map as input to i.atcorr with the visibility option.
The corresponding options in the 6s input file are then ignored by i.atcorr.
>
> Would visibility values in the 6s parameter file be overwritten if a AOD
map is provided to i.atcorr?
>
> The i.atcorr manual[1] is not particularly clear on this…
>
> In fact handling of visibility map is mentioned as a remaining
documentation issue in the manual.

such a long manual, and still not complete...

If a visibility map is provided, the parameters regarding AOD at 550nm in
the 6s input file are ignored. I added a short note in trunk r72917.

Markus M
>
>
>
> Maybe something you could have a look at in your GSoC project, Roberta?
>
>
>
> Cheers
>
> Stefan
>
>
>
> 1: https://grass.osgeo.org/grass75/manuals/i.atcorr.html
>
>
>
> From: Markus Metz <markus.metz.giswork at gmail.com>
> Sent: torsdag 28. juni 2018 14:09
> To: Stefan Blumentrath <Stefan.Blumentrath at nina.no>
> Cc: Yann Chemin <dr.yann.chemin at gmail.com>; mlennert at club.worldonline.be;
GRASS-dev <grass-dev at lists.osgeo.org>; Roberta Fagandini <
robifagandini at gmail.com>
>
>
> Subject: Re: [GRASS-dev] compile 6S library in GRASS
>
>
>
>
>
> On Thu, Jun 28, 2018 at 2:03 PM, Stefan Blumentrath <
Stefan.Blumentrath at nina.no> wrote:
> >
> > Just one quick follow up question regarding your wild guess:
> >
> >
> >
>
> > With a raster map option, the module would have to make assumptions on
units / scale of values in the map (documented in the manual), so in the
further process e.g. average or median could be extracted (r.univar) and
fed to 6s input file, right?
>
>
>
> no, i.atcorr accepts a visibility raster map as input, equivalent to
aerosol optical depth at 550nm.
>
>
>
> Note that internally i.atcorr converts AOD at 550nm to visibility with
>
> v = exp(-log(taer55 / 2.7628f) / 0.79902f);
>
>
>
> Markus M
>
> >
> >
> >
> > Cheers
> >
> > Stefan
> >
> >
> >
> >
> >
> > From: grass-dev <grass-dev-bounces at lists.osgeo.org> On Behalf Of Yann
Chemin
> > Sent: torsdag 28. juni 2018 13:38
> > To: mlennert at club.worldonline.be
> > Cc: Markus Metz <markus.metz.giswork at gmail.com>; GRASS-dev <
grass-dev at lists.osgeo.org>; Roberta Fagandini <robifagandini at gmail.com>
> > Subject: Re: [GRASS-dev] compile 6S library in GRASS
> >
> >
> >
> > a wild guess: specify a raster input option for AOT (alongside other
options), let user find its image source and use it.
> >
> >
> >
> > Very limited requirement for the GSoC student, most latitude for the
the modules user.
> >
> >
> >
> > ----------
> > Dr. Yann Chemin
> >
> > Freelancer
> >
> > +33 7 83 85 5234
> >
> > 3 Toulmelin, 56400 Plumergat, FR
> >
> > https://www.paypal.me/yannchemin
> >
> >
> >
> >
> >
> > On Thu, 28 Jun 2018 at 13:35, Moritz Lennert <
mlennert at club.worldonline.be> wrote:
> >
> > On 28/06/18 12:17, Roberta Fagandini wrote:
> > > I'm not an expert in MODIS data so if someone wants to give
> > > suggestions about how to retrieve the AOT from these data, I will
> > > definitely add this option too.
> >
> > I'm not an expert, and MarkusM can probably provide you with more info,
> > but you can already see https://lpdaac.usgs.gov/node/1265.
> >
> > Moritz
> >
> >
> > _______________________________________________
> > grass-dev mailing list
> > grass-dev at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-dev
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