[GRASS-dev] i.gensiget: "Unreliable clustering. Try a smaller initial number of clusters"
Nikos Alexandris
nik at nikosalexandris.net
Fri Jul 5 17:41:00 PDT 2013
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
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