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

[Nikos Alexandris]

Blumentrath, Stefan wrote:
> Hi Nikos

Hallo Stefan,

> I had similar problems with this module. My experience with i.gensigset is,
> that it can be quite sensitive for how training areas aredistributed and
> how well they can be distinguished.

Interesting.  The only "failure" I was able, so far, to verify is that the 
training areas should not capture NULL pixels in the to-be-classified 
image(s).  Can't trace though my posts about this (few years back).


> I do not know the algorithm nor what exactly the problem was in my case. But
> I solved this error message by adjusting the training areas in a way that I
> added training areas for classes where I had a relatively lower number of
> pixels (compared to the number of pixels in other classes) in a first try
> and removed/reshaped possibly conflicting training units in order to avoid
> overapp in subsignatures across classes.

Will try (soon I think == within the next 2 weeks).


> I do not know how you generated your training areas, but maybe you have a
> chance to try adjusting them...

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.


> Hope that helps and I am interested in what does the trick for you or what
> other, more experienced, users say on that topic...

Will feed-back when the time comes.

Danke, Nikos