[GRASS-user] Grass 7.6 i.segment minsize working?

[Jamille Haarloo]

Thank you Markus,

I used this data:
https://drive.google.com/file/d/1xrLJY5aZLKE-ja51wKRX_CKKcUtIiy16/view?usp=sharing
(excluding band 6. I used band 1-5 as group)

The parameters:
i.segment.hierarchical group=S2bands_VV at LUPS thresholds=0.1, 0.2
output=hier_segmS2 minsizes=20 memory=4000 iterations=30

i.segment --overwrite group="S2bands_VV" output="SegmS2_02_20"
band_suffix="Modified" threshold=0.2 radius=1.5 method="region_growing"
similarity="euclidean" minsize=20 memory=4000 iterations=50
goodness= "goodn_of_fit_SegmS2_02_20"

g.region -p

projection: 1 (UTM)
zone:       21
datum:      wgs84
ellipsoid:  wgs84
north:      620222.920747
south:      617573.079721
west:       782605.544297
east:       785903.817009
nsres:      0.49997
ewres:      0.49996555
rows:       5300
cols:       6597
cells:      34964100


On Tue, Jun 18, 2019 at 5:04 PM Markus Metz <markus.metz.giswork at gmail.com>
wrote:

>
>
> On Tue, Jun 18, 2019 at 3:31 PM Jamille Haarloo <j.r.haarloo at gmail.com>
> wrote:
> >
> > Dear Grass members,
> >
> > I have been testing i.segment and i.segment.hierarchical on a small
> region with Sentinel bands. However, the results consistently include
> segments of just one pixel even-though minimal segment sizes of 10 and 20
> were indicated. The final run with minsize 20 created 8247 segments.
> > There were no errors nor warnings, and I couldn't find the i.segment
> script to review it.
>
> It is here:
> https://github.com/OSGeo/grass/tree/releasebranch_7_6/imagery/i.segment
>
> > I also tried with a minsize of one (1). The result looks similar with
> even less segments created - a total of  8160.
> > I tried with Grass Gis 7.6.0 and 7.6.1(download of yesterday).
>
> I tested in the North Carolina sample dataset with
> g.region -p rast=lsat7_2002_10
>
> using default minsize 1
> i.segment group=lsat7_2002_10,lsat7_2002_20,lsat7_2002_30,lsat7_2002_40
> thresh=0.05 out=lsat7_2002_min1
> --> i.segment complete. Number of segments created: 29399
>
> r.info -r lsat7_2002_min1
> min=1
> max=29399    <-- as expected
>
> using minsize=20
> i.segment group=lsat7_2002_10,lsat7_2002_20,lsat7_2002_30,lsat7_2002_40
> thresh=0.05 out=lsat7_2002_min20 minsize=20
> --> i.segment complete. Number of segments created: 2114
>
> r.info -r lsat7_2002_min20
> min=1
> max=2114    <-- as expected
>
> r.stats -c lsat7_2002_min20 | sort -k 2n | head
> 1025 20
> 1081 20
> 109 20
> 1117 20
> 1220 20
> 1305 20
>
> The given minimum segment size is in this test respected.
>
> Can you provide test data, region settings and parameters for i.segment to
> reproduce?
>
> Markus M
>
>
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