[GRASS-dev] reg i.pca module

[Markus Neteler]

On Thu, Feb 7, 2013 at 10:21 AM, Rashad M <mohammedrashadkm at gmail.com> wrote:
> Hi,
>
> I am trying to develop a tool for grass which is one of the things that
> xgobi[1] does. The idea is from Markus Neteler which is to identify pure
> pixel/end members from a PCA plot.

Background: it has been shown that pure pixels (endmembers) for spectral
unmixing are in the corners of the PCA feature space.

Attached an old drawing from my master thesis (1999) about the topic.

> Since i.pca transforms pixel position is lost.

This is why I used the coordinates as raster pixel *attributes* in XGOBI
to relate original pixels and PCA transformed pixels to each other.

The east, north coordinates I stored as attributes, the PCA in XGOBI
supported to keep them alongside the transformed pixel. Solved.

What's needed in GRASS: That the i.pca modules allows to keep
raster pixel text labels in which the original position could be stored.
Then a little parsing of the category label and the original position
of a PCA transformed pixel could still be retrieved.

Hope this explains what I did those days in my thesis.

cheers
Markus
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