[postgis-users] Repost: Intersection not working properly

[Webb Sprague]

Can you post astext() version of your geometries and srids so the list
members can try to reproduce?  (Disregard if you already did in your
last email).

-W

On 10/21/07, Craig Feuerherdt <craigfeuerherdt at gmail.com> wrote:
> This is a re-post of a message from last week. I still have not resolved the
> issue.
>
> I am trying to clip one table using the features in another. My query is as
> follows;
>
> drop table bio.bnd_evc;
> create table bio.bnd_evc as
> select a.buf_dist, b.bio_no, b.bio_code, b.evc, b.constcde, b.consstat ,
> b.density, intersection(a.the_geom, b.the_geom) as the_geom
> from bio.bnd_buf as a, bio.evc as b
> where a.the_geom && b.the_geom
> and a.buf_dist = 1
> and intersects(a.the_geom, b.the_geom)
>
> Both tables have a GIST index. The query returns a table, however there are
> several polygons from the evc table, within the bnd_buf table, that are
> missing. I thought those missing polygons may have had invalid geometries
> (which is not the case as isvalid(evc.the_geom) returns TRUE for all
> geometries) and buffered the evc layer by 0, however this made no
> difference. One of the missing polygons is completely contained by the
> selected feature in bnd_buf, but other features that are also completely
>  contained have been selected. The resultant table also shows (in QGIS)
> polygons where there were no evc polygons.
>
> I am at a loss to explain what is going on nor how to correct it.
>
> Thanks in advance,
>
>  Craig Feuerhedt
>
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