[GRASS-user] i.atcorr with Sentinel2

Mon Dec 18 07:13:58 PST 2017

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 <
mlennert at 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 at p_Sentinel4Nature_S2_Oslo
>>   +---------------------------------------------------------
>> -------------------+
>>   | Map:      test_B02 at 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 at p_Sentinel4Nature_S2_Oslo range=1,28000
>> elevation=dem_10m_25833 at 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 at p_Sentinel4Nature_S2_Oslo
>>   +---------------------------------------------------------
>> -------------------+
>>   | Map:      test_B02_atcorr at 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 at p_Sentinel4Nature_S2_Oslo" range=1,28\
>>   |    000 elevation="dem_10m_25833 at 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 <zoficimburova at gmail.com
>> <mailto:zoficimburova at 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 <neteler at osgeo.org
>>     <mailto:neteler at osgeo.org>> wrote:
>>
>>
>>         On Dec 15, 2017 3:54 PM, "Žofie Cimburová"
>>         <zoficimburova at gmail.com <mailto:zoficimburova at 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
>>
>>
>>
>>
>>
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>>
>>
>
>
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