[GRASS-user] i.atcorr returns all NULL values

[Brian Walters]

Hello,
I'm using i.atcorr to perform atmospheric corrections on Landsat 5 TM data
and something peculiar seems to happen arbitrarily to some of the data.  For
the most part everything works fine, but for some of the bands the result is
a raster layer that is filled with nothing but NULL values.  For example, I
have images from 3 dates over the same area.  All the layers are integer and
scaled from 0 - 255, and the elevation layer I'm using is also integer.  All
bands from the first date and the last date run through i.atcorr with no
problems, as do bands 3, 4, 5, & 7 from the middle date.  However, bands 1
and 2 from the middle date return all NULLs.  I have tried many things,
including running i.atcorr on a small subset of the band (same result),
changing the date by a day or two in the* *icnd.txt file (same result), and
changing the band to TM5 band 3 in the icnd.txt file (this ran normally).  I
can't figure out why bands 1 and 2 would run normally on two of my dates and
why bands 3-5,7 would run on this particular date yet bands 1 and 2 result
in the NULL values.  Anyone else have this problem and any clues as to why
i.atcorr is doing this?  Any help would be greatly appreciated.

Here is the text of my icnd.txt file for band 1:
7
6 23 15.966 -84.165 44.587
2
1
14.16
-0.262
-1000
25

The command I'm running:
i.atcorr -r -o iimg=peak_B1_toa at mich
ialt=elevation at michicnd=atcorr_paramfiles/atcorr_peak_B1.txt
oimg=peak_B1_atm_corr

I'm using GRASS version 6.4.0RC6

Thanks,
Brian
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