[GRASS-user] R: NULL values as output of i.atcorr

[Moritz Lennert]

On 27/01/22 14:01, ilaria.ferrando87 at gmail.com wrote:
> Dear Moritz,
> thank you for your reply.
> I tried with and without the -r flag and the results is the same.

I reformulate this part of the question then: what exactly is the 
content of immagine at mapset ? Please provide the output of

r.info map=immagine at mapset

> Please find attached the parameters of the file 22giugno2020_b4.txt:
> 
> 26
> 6 22 17.05 9.68728523 43.75514951
> 2
> 1
> 0
> -0.293

Are you sure this should be a negative number ? This should be 
visibility in km IIRC.

> -1000
> 182


Moritz
> 
> -----Messaggio originale-----
> Da: Moritz Lennert <mlennert at club.worldonline.be>
> Inviato: giovedì 27 gennaio 2022 13:22
> A: Ilaria Ferrando <ilaria.ferrando87 at gmail.com>; Maris Nartiss <maris.gis at gmail.com>
> Cc: GRASS user list <grass-user at lists.osgeo.org>
> Oggetto: Re: [GRASS-user] NULL values as output of i.atcorr
> 
> On 26/01/22 19:50, Ilaria Ferrando wrote:
>> Dear Māris,
>> Thank you for your reply.
>> Yes, the image is inside the computational region.
>> Any other ideas?
> 
> 
> 1) Are you sure your input data is reflectance (-r flag used) ?
> 2) Could you provide us with the contents of the 22giugno2020_b4.txt file ?
> 
> Moritz
> 
>>
>> Il mer 26 gen 2022, 19:45 Maris Nartiss <maris.gis at gmail.com
>> <mailto:maris.gis at gmail.com>> ha scritto:
>>
>>      One thing to always check – does your computational region contain
>>      data you are analysing? Try to run `g.region rast=immagine` before
>>      running i.atcorr.
>>
>>      Māris.
>>
>>      trešd., 2022. g. 26. janv., plkst. 18:13 — lietotājs
>>      <ilaria.ferrando87 at gmail.com <mailto:ilaria.ferrando87 at gmail.com>>
>>      rakstīja:
>>       >
>>       > Dear all,
>>       >
>>       > I am having troubles in processing a Sentinel-2 image with i.atcorr.
>>       >
>>       > The command I use is the following:
>>       >
>>       > i.atcorr -r -input=immagine at mapset range=0,10000
>>      parameters=C:\...\22giugno2020_b4.txt output=immagine_atcorr rescale=0,1
>>       >
>>       > and I obtain this output:
>>       >
>>       > wavelength less than 0.25 micron:
>>       >
>>       > let's take s(l)=s(0.25)
>>       >
>>       > Atmospheric correction...
>>       >
>>       > Atmospheric correction complete.
>>       >
>>       >
>>       >
>>       > The map I obtain is constituted by pixels with 6.669033e-34 values.
>>       >
>>       > Can anyone explain the meaning of the output and why I obtain a
>>      NULL value corrected map?
>>       >
>>       > Thank you for your support.
>>       >
>>       >
>>       >
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