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

[Markus Neteler]

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