[GRASS-dev] i.segment on panchromatic band of Worldview 2 scene: what resources are necessary to complete segmentation ?

[Moritz Lennert]

Hello,

In parallel to the discussion going on in another thread, I have a 
question concering the segmentation of another Worldview 2 scene:

I first used all 8 multispectral bands and managed to get a series of 
results with increasing thresholds in very reasonable running times. The 
region was as follows:

 > g.region -p
projection: 1 (UTM)
zone:       -36
datum:      wgs84
ellipsoid:  wgs84
north:      7251172
south:      7234772
west:       333792
east:       350192
nsres:      2
ewres:      2
rows:       8200
cols:       8200
cells:      67240000

and the command line:

i.segment group=xs out=seg_xs minsize=2 memory=3072 threshold=0.05 (and 
thresh=0.1 and 0.2 in successive runs using the results of the previous 
run as seeds).

Now, I would like to test segmentation of just the panchromatic band. 
This means the following region settings:

projection: 1 (UTM)
zone:       -36
datum:      wgs84
ellipsoid:  wgs84
north:      7251172
south:      7234772
west:       333792
east:       350192
nsres:      0.5
ewres:      0.5
rows:       32800
cols:       32800
cells:      1075840000

Trying to run with the following command line on my i3, 8GB RAM machine:

i.segment group=pan out=seg_pan_005 threshold=0.05 memory=3072

had the process running for almost 13 hours with it then becoming 
apparently stuck in the fourth pass at 10%. At that point the percent 
didn't change for over an hour, so I decided to kill the process. Can I 
assume that I'm here above the capacities of my machine ? Is there 
anything (besides working on a smaller subsample of the image) that I 
can do to make it work ? What kind of resources would I need to be able 
to run such a segmentation?

I guess I'll have to move these kinds of treatments to our university 
supercomputer, but I first have to get them to install GRASS...

Moritz