Re: i.atcorr with Sentinel2

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.)

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 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_20160907T044118_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 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 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"
o\
 |    utput="test_B02_atcorr2" rescale=0,255

 |

 +----------------------------------------------------------------------------+



On Fri, Dec 15, 2017 at 5:12 PM, Žofie Cimburová <[email protected]>
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 <[email protected]> wrote:
>
>>
>> On Dec 15, 2017 3:54 PM, "Žofie Cimburová" <[email protected]>
>> 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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