Dear Moritz, According to https://earth.esa.int/web/sentinel/user-guides/sentinel-2-msi/product-types , the L1C product I am using already is in top of atmosphere reflectance, so this should not be the problem (?). I tried running i.atcorr both with and without the -r flag.
Zofie On Mon, Dec 18, 2017 at 3:35 PM, Moritz Lennert < mlenn...@club.worldonline.be> wrote: > On 18/12/17 13:14, Žofie Cimburová wrote: > >> Hi all, >> Now the 6S parameters are complete, but the output map contains only >> NULLs, no matter what combinations of input parameters and flags I use. >> Have anyone encountered the same issue? (Info below.) >> > > In the i.atcorr man page it says: > > "If flag -r is used, the input raster data are treated as reflectance. > Otherwise, the input raster data are treated as radiance values" > > IIUC, your data is still in DN. You might want to try to transform this > into radiance values before sending it into i.atcorr. > > Moritz > > >> Thanks again. >> Zofie >> >> ---------------------------------------- >> Version: >> g.version -g >> version=7.4.0RC1 >> date=2017 >> revision=exported >> build_date=2017-11-18 >> build_platform=x86_64-pc-linux-gnu >> build_off_t_size=8 >> >> ---------------------------------------- >> Region: >> g.region -p >> projection: 1 (UTM) >> zone: 33 >> datum: etrs89 >> ellipsoid: grs80 >> north: 6653695 >> south: 6643685 >> west: 256495 >> east: 266505 >> nsres: 10 >> ewres: 10 >> rows: 1001 >> cols: 1001 >> cells: 1002001 >> >> ---------------------------------------- >> Input data: Sentinel2 L1C product B02 (tried with B01 too) >> r.info <http://r.info> map=test_B02@p_Sentinel4Nature_S2_Oslo >> +--------------------------------------------------------- >> -------------------+ >> | Map: test_B02@p_Sentinel4Nat Date: Wed Dec 6 12:06:39 2017 >> | Mapset: p_Sentinel4Nature_S2_Oslo Login of Creator: >> stefan.blumentr >> | Location: ETRS_33N >> | DataBase: /data/grass >> | Title: S2A_OPER_PRD_MSIL1C_PDMC_20160 >> 907T044118_R008_V20160905T104022_2 >> | Timestamp: none >> |--------------------------------------------------------- >> -------------------| >> | >> | Type of Map: raster Number of Categories: 0 >> | Data Type: CELL >> | Rows: 1001 >> | Columns: 1001 >> | Total Cells: 1002001 >> | Projection: UTM (zone 33) >> | N: 6653695 S: 6643685 Res: 10 >> | E: 266505 W: 256495 Res: 10 >> | Range of data: min = 1 max = 28000 >> | >> | Data Description: >> | generated by r.in.gdal >> +--------------------------------------------------------- >> -------------------+ >> >> ---------------------------------------- >> 6s file: >> 25- geometrical conditions=Sentinel-2A >> 9 5 10.6728 10.73413 59.90647- month day hh.ddd longitude latitude >> 4 - atmospheric model=subarctic summer >> 3- aerosol model=urban >> 50- visibility [km] (aerosol model concentration) (this is estimated, I >> also tried with AOD specified) >> -0.055- mean target elevation above sea level [km] >> -1000- sensor height >> 166- Sentinel2A Blue band B2 (440nm - 535nm) >> >> ---------------------------------------- >> Command: >> i.atcorr input=test_B02@p_Sentinel4Nature_S2_Oslo range=1,28000 >> elevation=dem_10m_25833@p_Sentinel4Nature_S2_Oslo parameters=/home/ >> NINA.NO/zofie.cimburova/Sentinel4Nature/DATA/6s.txt < >> http://NINA.NO/zofie.cimburova/Sentinel4Nature/DATA/6s.txt> >> output=test_B02_atcorr >> >Atmospheric correction... >> >Atmospheric correction complete. >> >> (I am not sure about the range parameter, tried with 0,255 too. The DEM >> contains no NULLs. Also tried running with -r and -a flags.) >> >> ---------------------------------------- >> Output: >> r.info <http://r.info> map=test_B02_atcorr@p_Sentinel4Nature_S2_Oslo >> +--------------------------------------------------------- >> -------------------+ >> | Map: test_B02_atcorr@p_Sentinel4N Date: Mon Dec 18 13:10:14 >> 2017 >> | Mapset: p_Sentinel4Nature_S2_Oslo Login of Creator: >> zofie.cimburova >> | Location: ETRS_33N >> | DataBase: /data/grass >> | Title: test_B02_atcorr2 >> | Timestamp: none >> |--------------------------------------------------------- >> -------------------| >> | >> | Type of Map: raster Number of Categories: 0 >> | Data Type: FCELL >> | Rows: 1001 >> | Columns: 1001 >> | Total Cells: 1002001 >> | Projection: UTM (zone 33) >> | N: 6653695 S: 6643685 Res: 10 >> | E: 266505 W: 256495 Res: 10 >> | Range of data: min = -nan max = -nan >> | >> | Data Description: >> | generated by i.atcorr >> | >> | Comments: >> | i.atcorr input="test_B02@p_Sentinel4Nature_S2_Oslo" range=1,28\ >> | 000 elevation="dem_10m_25833@p_Sentinel4Nature_S2_Oslo" para\ >> | meters="/home/NINA.NO/zofie.cimburova/Sentinel4Nature/DATA/6s.txt >> <http://NINA.NO/zofie.cimburova/Sentinel4Nature/DATA/6s.txt>" o\ >> | utput="test_B02_atcorr2" rescale=0,255 >> | >> +--------------------------------------------------------- >> -------------------+ >> >> >> >> On Fri, Dec 15, 2017 at 5:12 PM, Žofie Cimburová <zoficimbur...@gmail.com >> <mailto:zoficimbur...@gmail.com>> wrote: >> >> Dear Markus, >> thanks for your reply, this is exactly what I need to know! >> >> Best, Zofie >> >> On Fri, Dec 15, 2017 at 5:09 PM, Markus Neteler <nete...@osgeo.org >> <mailto:nete...@osgeo.org>> wrote: >> >> >> On Dec 15, 2017 3:54 PM, "Žofie Cimburová" >> <zoficimbur...@gmail.com <mailto:zoficimbur...@gmail.com>> wrote: >> > >> > Dear all, >> > I am trying to use i.atcorr (GRASS 7.4) to apply atmospheric >> corrections for Sentinel 2 data. The documentation provides a great help, >> but there are two points I am not sure about - > >> > - I don't need the atmospheric correction to be applied to the >> whole scene, so I only imported a small clip of the scene to GRASS. What >> longitude and latitude shall I then specify in the 6S parameters? >> >> I'd use the center coordinates of the clipped area. >> >> > Or is it necessary to apply the corrections to the entire scene? >> >> No since it is a pixel based algorithm. >> >> > - How can I estimate the value of visibility (aerosol model >> concentration)? >> There are AERONET data online somewhere which might be the best >> choice. >> >> Markus >> >> >> >> >> >> _______________________________________________ >> grass-user mailing list >> grass-user@lists.osgeo.org >> https://lists.osgeo.org/mailman/listinfo/grass-user >> >> > >
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