[postgis-users] intersection

[strk at refractions.net]

You're probably looking for the && operator.
'intersects' detect *topological* intersection, so a point inside
a polygon's hole do not intersect it, but overlaps (&&) it's bounding
box.

--strk;

On Fri, Mar 04, 2005 at 02:18:04PM -0700, Sean M. Montague wrote:
> I think I've figured out the problem.  Does PostGIS not intersect
> polygons with holes?  If I do not use thu intersection, everything is
> fine.  But if I try to intersect my city layer, with many holes, then
> the select fails.
> 
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Sean
> M. Montague
> Sent: Friday, March 04, 2005 1:03 PM
> To: PostGIS Users Discussion
> Subject: [postgis-users] intersection
> 
> I've successfully intersected polygons, but wonder what limitations it
> has.  For instance, I've returned the dimensions of a county, adjusted
> the bb to fit my embedded SVG viewBox, and used these dimensions to clip
> the county layer to fill the entire viewBox.  This way I have a perfect
> fit every time, discarding the rest of the state.  But now I want to add
> a layer such as city boundaries or parks.  The intersection doesn't seem
> to work with these layers.  I'm assuming it is because they don't fill
> the entire bb, they're islands.  Is this the case?  If so is there an
> alternative?  Thanks.
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