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_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
<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
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