[GRASS-user] clipping line data to a polygon

[Vincent BAIN]

Sorry if my answer is a bit out of the scope of Grass :
from time to time I use OpenJump GIS. For this type of task (don't ask
me why) it's incredibly faster. Maybe any of you could explain this
difference ?

VB

Le vendredi 17 août 2007 à 17:21 +1200, Hamish a écrit :
> > 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?
> > 
> Hamish:
> > 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?)
> 
> 
> Hamish
> 
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