[GRASS-dev] i.segment error: Ri is 0

[Moritz Lennert]

Hi Eric and Markus,

Trying to use i.segment in grass7 checked out and compiled a few days 
ago (rev 56918), I came upon the following error and the resulting 
segments file was not created. I can file this as a bug report, but 
wanted your feedback first to see if I'm misusing i.segment somehow. I 
haven't been able to find the error in the source code.

command line:
time i.segment group=xs out=seg_xs minsize=2 memory=3072 threshold=0.2 --o

error:
Segmentation converged after 16 iterations.
Merging segments smaller than 2 cells
ERREUR :Ri is 0

This is on a mosaic of Worldview 2 images with region specs as follows:

 > g.region -p
projection: 1 (UTM)
zone:       33
datum:      wgs84
ellipsoid:  wgs84
north:      4876400
south:      4849792
west:       610056
east:       634648
nsres:      2
ewres:      2
rows:       13304
cols:       12296
cells:      163585984

The mosaic is only a narrow band within that region, so that actually 
there are only 34,755,878 non-null cells.

Any hints ?

Moritz