[GRASS-dev] i.pca

[Brad Douglas]

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.


-- 
Brad Douglas <rez touchofmadness com>                    KB8UYR/6
Address: 37.493,-121.924 / WGS84    National Map Corps #TNMC-3785