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 <[email protected]>: > 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 > <[email protected]> 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/ _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
