* Micha Silver <[email protected]> [2015-05-29 16:32:24 +0300]: > I'm trying to do atmospheric correction on some landsat 8 tiles. I have > successfully prepared ToA reflectance (with i.landsat.toar -r ).
i.landsat.toar -r would give Radiances. Would you please confirm that the above wasn't simply a "typo"? And what is the type of the output? Uncorrected, or any of the DOS corrected types? > Now when I run i.atcorr, I first get the range parameters by extracting > the actual minimum,maximum values from each band. And I set the rescale > parameter to 0,1. However this warning appears: > > > r.info -r lc81740392014220_toa_refl2 > min=0.0749609194287782 > max=0.649816591520163 > > i.atcorr -r input=lc81740392014220_toa_refl2 output=atcorr_test > elevation=ast_dem parameters=6S_lc81740392014220_b2.txt > range=0.0749609194287782,0.649816591520163 rescale=0,1 > WARNING: Scale range length should be > 0; Using default values: [0,255] > Atmospheric correction... Here, I guess that Reflectance is (correctly) the input imagery. > > > and the band gets values much larger the the desired 0,1 range for > reflectance. How should this be dealt with? Is it really necessary to > set the range to the exact min/max values for each band? We should set a clear set of Question and Answers, and document it in the wiki for all of these issues. > or can I just > choose arbitrary range values that cover the min/max for all the bands > I'm using? Not sure. > (BTW, the above seems to work OK if I use ToA *radiance*, and a specific > set of range values for each band, again based on the actual min/max for > that band) I think this is correct, meaning going from DN > Radiance (via i.landsat.toar), then from Radiance > Reflectance (via i.atcorr). Can we compare the output of i.landsat.toar and the output of a custom r.mapcalc formula for conversions from DN > Radiance > Reflectance? I have too seen sometimes, for Landsat8 data, heavily skewed histograms for Landsat8 reflectances, ranging in [0, 1] which might or might not be ok. Nikos _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
