Thank you very much for your support! I will keep you update on my (I hope) progresses!
-----Messaggio originale----- Da: Moritz Lennert <mlenn...@club.worldonline.be> Inviato: venerdì 28 gennaio 2022 12:07 A: ilaria.ferrand...@gmail.com; 'Maris Nartiss' <maris....@gmail.com> Cc: 'GRASS user list' <grass-user@lists.osgeo.org> Oggetto: Re: R: R: R: [GRASS-user] NULL values as output of i.atcorr On 28/01/22 10:55, ilaria.ferrand...@gmail.com wrote: > Thank you Moritz, I will do some research on visibility (aerosol model > concentration) to put a reasonable value there (any suggestion is > appreciated, also regarding references to look at). The man page suggests https://aeronet.gsfc.nasa.gov/. > How can I transform digital number into radiance/reflectance? This information should be in the metadata that accompanies the Sentinel data. I haven't worked with this data in a couple of years, so don't remember. However, in the doc on https://docs.sentinel-hub.com/api/latest/data/sentinel-2-l2a/, you can read: For Sentinel-2 optical data, the relation between DN and REFLECTANCE (default unit) is: DN = 10000 * REFLECTANCE. Moritz > Thank you very much for your precious help! > > -----Messaggio originale----- > Da: Moritz Lennert <mlenn...@club.worldonline.be> > Inviato: giovedì 27 gennaio 2022 17:50 > A: ilaria.ferrand...@gmail.com; 'Maris Nartiss' <maris....@gmail.com> > Cc: 'GRASS user list' <grass-user@lists.osgeo.org> > Oggetto: Re: R: R: [GRASS-user] NULL values as output of i.atcorr > > On 27/01/22 14:54, ilaria.ferrand...@gmail.com wrote: >> The output of r.info is the following >> >> r.info map=immagine@mapset >> >> +----------------------------------------------------------------------------+ >> | Map: immagine@mapset Date: Tue Nov 30 12:51:12 2021 | >> | Mapset: mapset Login of Creator: [...] | >> | Location: WGS84_UTM32 >> | >> | DataBase: C:\Users\[...]\grassdata | >> | Title: immagine >> | >> | Timestamp: none >> | >> >> |----------------------------------------------------------------------------| >> | >> | >> | Type of Map: raster Number of Categories: 0 >> | >> | Data Type: CELL >> | >> | Rows: 10980 >> | >> | Columns: 10980 >> | >> | Total Cells: 120560400 >> | >> | Projection: UTM (zone 32) >> | >> | N: 4900020 S: 4790220 Res: 10 >> | >> | E: 609780 W: 499980 Res: 10 >> | >> | Range of data: min = 0 max = 18876 >> | >> | >> | >> | Data Description: >> | >> | generato da r.in.gdal >> | >> | >> | >> | Comments: >> | >> | r.in.gdal -e input="C:\Users\[...]\T32TNP_2020062\ | >> | 2T100559_B04.jp2" output="immagine" memory=300 offset=0 num_digits=0 >> | >> | >> | >> >> +-------------------------------------------------------------------- >> +- >> -------+ > > This looks to me like the data is in digital number, not in radiance or > reflectance. You first have to translate it to one or the other before > feeding it to i.attcor. > >> >> Do you mean the sixth line of the file? From the i.atcorr help it is the >> "mean target elevation above sea level [km]", and it is correct that it is >> negative. >> I'm now wondering if the problem can be having put "0" for visibility >> (aerosol model concentration, fifth line). What do you think about it? > > I am speaking about the value '-0.293' in line 6 (and yes, my bad for > not paying attention to the value 0 in the line before). The man page > states: "If you have an estimate of aerosol optical depth, enter 0 for the > visibility and in a following line enter the aerosol optical depth at 550nm > (iaer means 'i' for input and 'aer' for aerosol), for example:" > So, if you have 0 on line 5, so line 6 is AOD and not mean target elevation > above sea level. > > In this case line 7 is the "mean target elevation above sea level [-km]" > with value -1000 :-). > > Moritz > > > > >> >> >> -----Messaggio originale----- >> Da: Moritz Lennert <mlenn...@club.worldonline.be> >> Inviato: giovedì 27 gennaio 2022 14:08 >> A: ilaria.ferrand...@gmail.com; 'Maris Nartiss' <maris....@gmail.com> >> Cc: 'GRASS user list' <grass-user@lists.osgeo.org> >> Oggetto: Re: R: [GRASS-user] NULL values as output of i.atcorr >> >> On 27/01/22 14:01, ilaria.ferrand...@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@mapset ? Please provide the output of >> >> r.info map=immagine@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 <mlenn...@club.worldonline.be> >>> Inviato: giovedì 27 gennaio 2022 13:22 >>> A: Ilaria Ferrando <ilaria.ferrand...@gmail.com>; Maris Nartiss >>> <maris....@gmail.com> >>> Cc: GRASS user list <grass-user@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....@gmail.com >>>> <mailto:maris....@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.ferrand...@gmail.com <mailto:ilaria.ferrand...@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@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. >>>> > >>>> > >>>> > >>>> > _______________________________________________ >>>> > grass-user mailing list >>>> > grass-user@lists.osgeo.org <mailto:grass-user@lists.osgeo.org> >>>> > https://lists.osgeo.org/mailman/listinfo/grass-user >>>> <https://lists.osgeo.org/mailman/listinfo/grass-user> >>>> >>>> >>>> _______________________________________________ >>>> grass-user mailing list >>>> grass-user@lists.osgeo.org >>>> https://lists.osgeo.org/mailman/listinfo/grass-user >>> >>> >> >> > > _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
