[GRASS-user] Questions: Clipping polygon layer to the outer boundary of another layer...

[Hamish]

Rick Reeves wrote:
> >> I'm using v.in.ogr to clip a polygon set (in this case, county 
> >> boundaries) to the boundary of a (rectangular) raster image.
> >>
> >> As far as I know, this is the only way to do this; I tried to
> >> create a new location with the same boundaries and import the
> >> polygon shapefile into the location, but clipping did not occur
> >> as expected.
> >>
> >> In any case, v.in.ogr did not clip the 'boundary polygons' to the
> >> the edge of the raster image, but included the entire polygon.
> >> Only excluded polygons completely outside of the bounding box
> >> are clipped.

Hamish:
> > I assume you used 'v.in.ogr spatial='. This works like v.select.
R:
> >> There MUST be a way to clip all polygons to the bounding box edge.
> >> Can any one suggest a way?
H:
> > v.in.region + v.overlay.

Moritz Lennert wrote:
> Or v.in.region + v.select if you don't wan't to merge attribute
> tables.

v.select will act the same way as 'v.in.ogr spatial=' (or a personal
favourite: 'v.in.ogr -r') which was what the original question was
hoping to avoid. ie v.select leaves features in or out, while v.overlay
both allows or omits features AND modifies any features which cross.


Hamish




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