[GRASS-dev] i.pca

[Brad Douglas]

On Fri, 2007-02-23 at 14:01 +0700, Yann wrote:
> 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. 

That could simply be a module option.  The calculations are trivial at
that point, but again, cannot be done without GRASS being aware of
metadata.

> 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?).

IIRC, r.in.aster does not work right and should really be renamed
i.in.aster.  i.landsat does not work correctly, either (it makes
assumptions it should not - eg. gain corrections, nadir angle,
etc.)...it has no metadata support and it looks like values were hard
coded.

> 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...

It is not practical to dump and parse a text file.  The GDAL API could
be used to get metadata from embedded formats like HDF.  Others are more
difficult.

IMO, the history file is not usable for storing metadata.  At least not
in it's present incarnation.  Making it so would require a rewrite of
many of the history functions.  It is probably easier to create a new
set of metadata functions that also includes much of the history
functionality and eventually deprecate the history file.

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

Not off-hand, no.


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