[GRASS-user] no output when running i.atcorr

Yann Chemin yann.chemin at gmail.com
Thu Feb 12 19:48:22 EST 2009


Hi,
i.atcorr has a test_suite in the source code,
it maybe a good start point.
Yann
------------------------
grass/imagery/i.atcorr/test_suite# ls
ETM4_400x400_atms_corr.hdr
ETM4_400x400.hdr
ETM4_atmospheric_input_GRASS.txt
ETM4.res
ETM4_400x400_atms_corr.raw
ETM4_400x400.raw
ETM4_atmospheric_input.txt
--------------------------

2009/2/13 Markus Neteler <neteler at osgeo.org>:
> Annekatrien,
>
> I am doing my first steps with i.atcorr now.
> I have added (with support from Yann Chemin) the specs for
> IRS 1C LISS which I need for a project. Also did some manual
> cosmetics.
>
> To warm up, I am doing first tests with the North Carolina
> test data set [1] which contains sample LANDSAT 7 data
> at reduced size.
>
> I observe that the module (or the procedure) is pretty slow,
> perhaps 5 pixels/second on my 2.5GHz box... said this, some
> comments below:
>
> On Fri, Jan 30, 2009 at 6:01 PM, Annekatrien Debien
> <annekatrien.debien at gmail.com> wrote:
>> Hi all,
>>
>> I want to do an atmospheric correction of my Landsat ETM+ images using the
>> i.atcorr module in Grass 6.3 on Ubuntu, but I never get an output.
>
> what does that precisely mean? It keeps you at 0% and calculates or
> it exists and no output?
>
> With NC data, I get (I hope I got the icnd.txt file right):
>
> # set region:
> g.region rast=lsat7_2002_10 -p
>
> # get central scene LatLong coordinates:
> g.region -gb | grep ll_c
> ll_clon=-78.70014170
> ll_clat=35.71092005
>
> cat icnd.txt
> 8                            - geometrical conditions=Landsat ETM+
> 5 24 15.50 -78.700 35.710    - month day hh.ddd longitude latitude
> ("hh.ddd" is a decimal hour GMT)
> 2                            - atmospheric mode=midlatitude summer
> 1                            - aerosols model=continental
> 50                           - visibility [km] (aerosol model concentration)
> -.600                        - target at 600m above sea level
> -1000                        - sensor on board a satellite
> 61                           - 1th band of ETM+ Landsat 7
>
> To be sure about the time (Landsat overpass, North Carolina is UTC-5):
> http://earthobservatory.nasa.gov/MissionControl/overpass.php
>
> # zoom to be faster for a test
> d.zoom
>
> # We can check the sun position with r.sunmask:
> r.sunmask -s --v lsat7_2002_10 out=dummy year=2002 \
>      month=5 day=24 hour=10 minute=30 sec=0 timezone=-5
> Using map center coordinates: 636732.750000 217569.000000
> Calculating sun position... (using solpos (V. 11 April 2001) from NREL)
> 2002.05.24, daynum 144, time: 10:30:00 (decimal time: 10.500000)
> long: -78.700150, lat: 35.710922, timezone: -5.000000
> Solar position: sun azimuth: 117.002434,
> sun angle above horz.(refraction corrected): 63.261234
> Sunrise time (without refraction): 05:08:34
> Sunset time (without refraction): 19:15:46
> No map calculation requested. Finished.
>
> # do the correction
> i.atcorr lsat7_2002_10 ialt=elevation icnd=icnd.txt \
>             oimg=lsat7_2002_10_atcorr
>
>
> * ****************************** 6s version 4.2b
> ****************************** *
> *                        geometrical conditions identity
>         *
> *                        -------------------------------
>         *
> *                        etm+     observation
>         *
> *
>         *
> *    month: 5 day: 24
>        *
> *    solar zenith angle:   26.71 deg  solar azimuthal angle:
> 117.09 deg   *
> *    view zenith angle:     0.00 deg  view azimuthal angle:
> 0.00 deg   *
> *    scattering angle:    153.29 deg  azimuthal angle difference:
> 117.09 deg   *
> *
>         *
> *                        atmospheric model description
>         *
> *                        -----------------------------
>         *
> *            atmospheric model identity :
>         *
> *                midlatitude summer  (uh2o=2.93g/cm2,uo3=.319cm-atm)
>         *
> *
>         *
> *            aerosols type identity :
>         *
> *                    Continental aerosols model
>         *
> *
>         *
> *            optical condition identity :
>         *
> *                 visibility :   50.00 km  opt. thick. 550nm :
> 0.1518       *
> *
>         *
> *                        spectral condition
>         *
> *                        ------------------
>         *
> *            etm+ 1
>         *
> *                value of filter function :
>         *
> *                 wl inf=    0.435 mic   wl sup=    0.520 mic
>        *
> *
>         *
> *                        target type
>         *
> *                        -----------
>         *
> *            homogeneous ground
>         *
> *              constant reflectance over the spectra     0.000
>        *
> *
>         *
> *                        target elevation description
>         *
> *                        ----------------------------
>         *
> *            ground pressure  [mb]        944.86
>        *
> *            ground altitude  [km]        0.600
>        *
> *                 gaseous content at target level:
>         *
> *                 uh2o=    2.189 g/cm2        uo3=    0.317 cm-atm
>        *
> *
>         *
> *                         atmospheric correction activated
>         *
> *                         --------------------------------
>         *
> 0%
>
> ... unfortunately the sun angle differs from the r.sunmask output.
> What's wrong?
>
>> When I
>> use a DEM in ialt, the continuous version or the categorized, of the region,
>> I just get "wavelength less than 0.25 micron              let's take
>> s(1)=s(0.25)". I don't insert an altitude value in my icdn file however,
>> since I've read that that value would overwrite the DEM. When I do put in an
>> altitude value, I get a list with the parameters for the 6S-algorithm, and
>> then 'percent complete', so that seems to be ok, but the algorithm stops
>> running, so I don't get a corrected image. Does anyone have experience with
>> this module, and help me with some tips, preferably so I can use my DEM
>> instead of one altitude value for the whole image?
>
> I have just tried on a tiny subset of lsat7_2002_10_atcorr but I see
> that the module uses the *entire* image:
>
> GRASS 6.5.svn (nc_spm_07):~ > g.region -p
> projection: 99 (Lambert Conformal Conic)
> ...
> rows:       18
> cols:       26
> cells:      468
>
> GRASS 6.5.svn (nc_spm_07):~ > fg
> i.atcorr lsat7_2002_10 ialt=elevation icnd=icnd.txt
> oimg=lsat7_2002_10_atcorr
> D0/0: Computed r0, c289
> D0/0: Computed r0, c290
> D0/0: Computed r0, c291  <- running out of current region!
>
> So some work is still needed.
>
> Markus
>



-- 
Yann Chemin
International Center of Water for Food Security
Office: http://www.icwater.org
Perso: http://www.freewebs.com/ychemin
YiKingDo: http://yikingdo.unblog.fr/


More information about the grass-user mailing list