[postgis-users] intersection

[Sean M. Montague]

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.