[GRASS-user] Estimating Albedo from Landsat

[José Miguel Barrios]

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
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