[GRASS-user] i.maxlik's reject versus i.segment's goodness

Vaclav Petras wenzeslaus at gmail.com
Sat Nov 15 18:21:41 PST 2014


Hi,

I executed the examples in i.cluster and i.maxlik manuals and also the
following i.segment command:

i.segment group=lsat7_2002 at w1-imagery output=lsat7_2002_segments
threshold=0.5 goodness=lsat7_2002_segments_goodness

(using the imagery group created in i.cluster example, otherwise unrelated)

I looked at goodness from i.segment and then reject from i.maxlik. I
noticed that there is some correlation between these two. Well, this is
quite okay since they are using same pixel values. However, then I noticed
that low values of goodness (-5000, ...) correlate with low values of
reject (1 == 1%). But the i.maxlik manual says that "1 = keep and 16 =
reject". Can somebody explain this to me and perhaps suggest improvement to
the manual? Shouldn't high rejection correlate with low goodness?

And also, less important thing, i.maxlik reject is an categorical map with
percentages reclassified to 16 classes. Does this have some practical
meaning or is this just an over-left from integer-only times?

Thanks,
Vaclav

http://grass.osgeo.org/grass71/manuals/i.cluster.html
http://grass.osgeo.org/grass71/manuals/i.maxlik.html
http://grass.osgeo.org/grass71/manuals/i.segment.html
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