[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
..
> > > 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:
..
> 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?

Still, we can use these approximations along with "method=dos3".  May I ask 
for confirmation(s)?

>From the manual:

DOS3: TAUv = exp[-t/cos(sat_zenith)], TAUz = exp[-t/sin(e)], Esky = rayleigh

Thanks, Nikos
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 230 bytes
Desc: This is a digitally signed message part.
URL: <http://lists.osgeo.org/pipermail/grass-user/attachments/20130315/884c8f77/attachment.pgp>