[GRASS-user] Visibility maps for i.at(mospherically)corr(ecting) Landsat imagery

[Nikos Alexandris]

Moritz:

> > >> If you can't find data, you can always use estimations such as in:
> > >> http://dx.doi.org/10.1364/AO.34.002765

Nikos:

> > > Thanks Moritz.  Although this looks a bit complex for quickly
> > > handcrafting a few scenes, isn't it?
 
Moritz:

> > The idea was not to do your own estimations, but to use those published
> > in this article (or others). See table 4 on page 6, where you can find
> > the following values for 550nm:
 
> > Tropical (15N): 0.09760
> > Midlatitude Summer (45N, July): 0.09745
> > Midlatitude Winter (45N, January): 0.09769
> > Subartic Summer (60N, July): 0.09688
> > Subartic Winter (60N, January): 0.09761
> > 1962 U.S. Standard: 0.09721
 
> > Obviously only approximations of mean values, but sometimes better than
> > nothing.

Nikos:
 
> Reference added in the wiki -- yet, still a subject to elaborate on.
> 
<http://grasswiki.osgeo.org/wiki/Atmospheric_correction#Atmospheric_correction>
 

Moritz,

during the CS in Genova we had a detailed discussion about that as well.

Yann (cc-ed) noted that Rayleigh scattering, obviously, is only a fraction of 
the whole thing that "retouches" the surface reflectance.  Maybe we should 
scratch the idea on using these estimations since they don't express Optical 
Depth entirely.  Or, find additional sources and add them up to these 
estimations?

Thanks, Nikos