[GRASS-dev] i.pca

[Yann]

Very long time ago (2000/2001?) i started writing a grass script to separate 
the Temperature and Emissivity of Aster. I failed, but the main lines of the 
equations where separated and laid down. Actually, higher level products were 
then available directly (and free at that time!) so it it was not worth the 
pain continuing the development.

Well, the emissivity/temperature splitting for Aster may actually be a nice 
module to develop. 

Besides, in grassaddons SVN, the conversion module for Landsat, the 
r.dn2ref.l7/r.dn2full.l7 could be nice to integrate with r.in.gdal (loosely 
or tight, is not the question now). I also have the r.dn2ref.ast that would 
also be nice to integrate with Aster import (r.in.aster?).

The Aster TOA reflectance conversion from DN should be possible by dumping 
gdalinfo into a temp.txt and parse that *somehow*. Unless we could try and 
use the GDAL API, but i am in unknown land here...

Brad any way you know to auto-calibrate i.atcorr?

any comments please or more than welcome.
Yann


On Friday 23 February 2007 13:27, Brad Douglas wrote:
> On Thu, 2007-02-22 at 22:24 -0700, Michael Barton wrote:
> > Brad,
> >
> > I had a chance to try this out tonight. It works very well. It seems to
> > go quite fast too. Here is a nice result of a PCA of a Terra ASTER bands
> > 1-9 (VNIR and SWIR) for part of the Phoenix metro area. I used d.his to
> > show PCA bands 1-3. The Salt River Indian Reservation agricultural fields
> > really stand out as do some of the mountain park areas.
> >
> > <http://www.public.asu.edu/~cmbarton/files/temp/phoenix_aster1-9_pca.jpg>
>
> Isn't ASTER great? ;-)  Too bad ALI/Hyperion costs $$.
>
> Is the pinkish area on the right edge supposed to be NULL data?  If so,
> I would make sure you ran 'r.null setnull=0'.  The non-null data may
> skew your results, slightly.  This was one of my motivations for the
> rewrite.
>
> Another of my pie-in-the-sky ideas is to write a module to adjust gains
> and calculate top of atmosphere reflectance or emissivity (where it can
> then be piped into i.atcorr).  Writing the module isn't difficult, but
> it requires metadata, which GRASS currently has no real method of saving
> or retrieving after r.in.gdal.  Currently, I have to look up metadata
> via 'gdalinfo' and manually run it through a series of r.mapcalc
> transactions.  Very tedious even if scripted.

-- 
Yann Chemin
Sainte-Anne d'Auray, France