[GRASS-user] i.atcorr with ToA reflectance

[Micha Silver]

I'm trying to do atmospheric correction on some landsat 8 tiles. I have 
successfully prepared ToA reflectance (with i.landsat.toar -r ).

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...


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? or can I just 
choose arbitrary range values that cover the min/max for all the bands 
I'm using?

(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)

Thanks,
Micha