The following bug has been logged online:

Bug reference: 2533
Logged by: Vania Bogorny
Email address: vbogorny (AT) gmail (DOT) com
PostgreSQL version: 7.4
Operating system: Windows XP
Description: PostGIS- envelope function returns wrong results
Details:

I would like to report an error with the evelope function in PostGIS (Geos
library).

According to the OGC, two geometries may only overlap if they are both of
the same type. I performed a query in PostGIS with 2 objects one polygon and
on multi-line. using the overlaps operation with the envelope function this
query returned 71 rows. It should return zero, since polygons and lines may
cross, an not overlap. Indeed, the crosses operations returns zero rows
among this objects using the evelope function.

Have you already presented a solution for the envelope operation or has this
problem not been reported previously.

Regards,
Vania

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On Sun, Jul 16, 2006 at 01:11:53PM +0000, Vania Bogorny wrote:
PostGIS and GEOS are separate projects from PostgreSQL. Questions
and bug reports should go to their respective mailing lists and
bug trackers.

http://postgis.refractions.net/support/

If you report this to the PostGIS project then please provide an
example query that demonstrates the behavior you're seeing. The
PostGIS folks might also want to know what versions of PostGIS and
GEOS you're running.

You mention that you're using envelope() but you don't say how --
are you converting the multilinestring to a polygon with envelope()
and using that polygon as one of the parameters to overlaps()?

--
Michael Fuhr

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