[GRASS-user] Estimating Albedo from Landsat

[Daniel Victoria]

Hi Jose,

I haven't tryed i.landsat.toar addon but from what I read in the wiki
(http://grass.osgeo.org/wiki/Atmospheric_correction) I could either
use i.landsat.toar or a DN - Radiance conversion formula that is
given...

Will try to recalculate the images, I might have done something wrong

Daniel

2010/8/2 José Miguel Barrios <jmbarriosg at gmail.com>:
> Hey Daniel
>
> I think the input map to be given in i.atcorr should not be the DN.
> Conversion to radiance or reflectance should be done before implementing the
> 6s algorithm.  Have you tried i.landsat.toar to obtain radiance values?
>
> Success!
>
> JM
>
>
> 2010/8/2 Daniel Victoria <daniel.victoria at gmail.com>
>>
>> Hi all,
>>
>> I'm trying to estimate albedo from landsat5 images but I'm getting
>> very strange result. Water bodies, for instance, are giving me an
>> albedo of 0.15 to 0.17, unusualy high.
>> Here is the procedure I'm doing
>>
>> 1) Convert TM images from grey level to radiance using the Lmax / Lmin
>> formula (parameters used given bellow [1])
>> 2) Apply 6S atmospheric correction, using standard tropical
>> atmosphere, continental aerosol mode
>> 3) Calculate shorwave albedo using Liang (2000) formula (based on
>> bands 1; 3; 4; 5 and 7)
>>
>> Since the albedo of water areas is comming out too high, I'm guessing
>> I messed up the i.atcorr procedure. I don't quite understand what
>> should be the input image (DN or Radiances?) and what is the output
>> image (reflectance scaled to 255?)
>>
>> Thanks
>> Daniel
>>
>>
>> [1]
>> Band    LMIN    LMAX
>> 1       -1,52   193
>> 2       -2,84   365
>> 3       -1,17   264
>> 4       -1,51   221
>> 5       -0,37   30,2
>> 7       -0,15   16,5
>> _______________________________________________
>> grass-user mailing list
>> grass-user at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/grass-user
>
>