[GRASS-user] clipping line data to a polygon

Hamish hamish_nospam at yahoo.com
Fri Aug 17 01:21:34 EDT 2007

> Mark wrote:
> > Is the best way to clip data to use the v.overlay command with the
> > "and" operator?
> > 
> > it works great, but seems quite slow on larger datasets. 
> > Additionally as an example, if i have topographic contour lines, and
> > i want to clip them to a polygon, and only want the topo line
> > attributes (elevation) outputted, is there a way to do this?  Is
> > there another way to clip line data to within a polygon that might
> > be a bit faster?
> run v.select, then v.overlay. That way the intensive v.overlay
> operation only happens for relevant vector features. Then it will
> speed up hugely.
> I wonder if v.select functionality could be built into v.overlay as a
> preprocessing step?

(see Radim's doc/vector/TODO in the source code; maybe splitting long
boundaries helps too?)


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