[GRASS-dev] compile 6S library in GRASS

Stefan Blumentrath Stefan.Blumentrath at nina.no
Thu Jun 28 01:53:18 PDT 2018


I would like to second Markus on that one.

We considered using AERONET for atmospheric correction in i.atcorr, but ended up using arbitrary / averaged values, cause AERONET data for our locations was very, very sparse and showed very high variation.

So, in a module, that compiles a 6s-parameter file, I would be happy if there was an option for providing manual values, ideally accompanied by fetching AOT values from other sources (e.g. AEORNET, MODIS).

Could be like in v.to.rast, where you have a “use” option (here e.g. with “value”, “aeronet”, “modis” choice), accompanied by “aot_value” to provide values manually, “aot_aeronet” option to provide input file or “aot_modis” which could be a raster map option the module extracts values from (producing that map(s) would be a user task).

Just a suggestion.

Kind regards,

From: grass-dev <grass-dev-bounces at lists.osgeo.org> On Behalf Of Markus Metz
Sent: onsdag 27. juni 2018 14:24
To: Roberta Fagandini <robifagandini at gmail.com>
Cc: GRASS developers list <grass-dev at lists.osgeo.org>
Subject: Re: [GRASS-dev] compile 6S library in GRASS

On Wed, Jun 27, 2018 at 2:16 PM, Roberta Fagandini <robifagandini at gmail.com<mailto:robifagandini at gmail.com>> wrote:
> I'm trying to create an automatic procedure to retrieve all the input parameters for the control file of i.atcorr.
> I need py6S because I want to automatically read and compute AOT at 550nm from an AERONET file.

With AOT you mean aerosol optical thickness right? This is user input to i.atcorr. There are various sources for AOT at 550nm, e.g. MODIS.

Anyway, it is probably much easier to to write your own routine to read the AERONET file and get the corresponding formula for AOT than to fight with 51821 lines of Fortran source code that is numerically unstable. Maybe I can help with getting AOT at 550nm from an AERONET file avoiding the Fortran version of 6S.

Markus M

> 2018-06-27 14:01 GMT+02:00 Moritz Lennert <mlennert at club.worldonline.be<mailto:mlennert at club.worldonline.be>>:
>> On 27/06/18 13:54, Roberto Marzocchi wrote:
>>> Il giorno mer 27 giu 2018 alle ore 13:47 Markus Metz <markus.metz.giswork at gmail.com<mailto:markus.metz.giswork at gmail.com> <mailto:markus.metz.giswork at gmail.com<mailto:markus.metz.giswork at gmail.com>>> ha scritto:
>>>     Hi Roberta,
>>>     On Wed, Jun 27, 2018 at 1:20 PM, Roberta Fagandini
>>>     <robifagandini at gmail.com<mailto:robifagandini at gmail.com> <mailto:robifagandini at gmail.com<mailto:robifagandini at gmail.com>>> wrote:
>>>      >
>>>      > Hi all!
>>>      > I need to compile the 6S library in GRASS in order to install the
>>>     python library Py6S [0].
>>>     do you really need Py6S? Can't you use i.atcorr instead?
>>> She use Py6S to calculate imput for i.atcorr
>> That seems a bit overkill: why use Py6S to then use i.atcorr ? What are you trying to get from Py6S ?
>> Moritz
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