[GRASS-dev] i.gensiget: "Unreliable clustering. Try a smaller initial number of clusters"

[Moritz Lennert]

On Sat, July 6, 2013 02:41, Nikos Alexandris wrote:
> It was a (quick) test only, I remember: created 3 sets of random points
> (some
> MASKed region, thus no NULL pixels included), buffered them to rational
> radiuses, labeled them (one 'val' for each set), grouped them, fed
> i.gensigset.
>

This might explain the issue ("unrelable clustering"): if your random
buffer areas are not real training areas representing specific homogenous
types of spectral responses, but completely random collections of spectral
signatures, how could any reliable generation of significanly
distinguished classes be achieved ?

You have to use training areas that actually have a meaning, i.e. be
representative of the different classes you wish to identify.

Moritz