[GRASS-dev] i.pca

[Brad Douglas]

Michael,

ASTER L1B data allocates 0 for dummy or null cells.  1 is reserved for
areas of zero radiance.  These and other values are defined in the ASTER
Users Handbook and is consistent with my experience.

You shouldn't have to go through all the extra effort to ensure deep
absorbers are 'visible'.

On Fri, 2007-02-23 at 01:08 -0700, Michael Barton wrote:
> Good point. But I can't just set 0=NULL, because there might well be 0's
> that mean something (e.g., water). If I really wanted to work with this
> image, I'd probably have to make a 'null mask' with the map calculator,
> setting to null any pixel that is 0 in all bands, and setting the rest to 1.
> Then I multiply each image by the null mask. If you have a faster way, I'd
> love to know about it.
> 
> Michael
> 
> On 2/22/07 11:27 PM, "Brad Douglas" <rez at touchofmadness.com> wrote:
> > 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.


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