[GRASS-user] v.overlay stops running

Hamish hamish_nospam at yahoo.com
Thu Feb 15 03:21:37 EST 2007

Tim Michelsen wrote:
> I am trying to overlay two huge polygons.
> After some time v.overlay dies or stops running:
> -------- Attaching islands ...
> Building topology ...
> Building areas:   31%
> then it stays at 31% for more than 30min. I suppose it has stopped.
> When I look at the files in directory I don't see any change on them
> for the same period.
> Why does it stop like that?

this may or may not work, but you might try running the big polygons
through "v.split vertices=5000" first.

see the "v.out.ogr" section of doc/vector/TODO in the source code for
the explanation:

"It would be useful to split long boundaries to smaller
pieces. Otherwise cleaning process can become very slow because
bounding box of long boundaries can overlap large part of the map (for
example outline around all areas) and cleaning process is checking
intersection with all boundaries falling in the bounding box."

Radim wrote v.split to work around this issue.


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