[postgis-users] error with overlay and disjoint

[strk at refractions.net]

Emilia, these error are usually due to invalid geometries:

	# select gid,isvalid(the_geom) from poligoni_geomunion;
	NOTICE:  Self-intersection
	NOTICE:  Self-intersection
	 gid | isvalid
	-----+---------
	 217 | f
	 219 | f
	(2 rows)

Have the geoms been produced by a call to geomunion (as the
name suggests) ? In this case it would help finding out the
original geometries as the bug is there.

--strk;

On Wed, Oct 19, 2005 at 08:15:04AM +0200, Emilia Venturato wrote:
> Hi all.
> Concerning my previous mail, I found the problem: it did not lay in the number 
> of records.
> Two the_geom have been made with GeomUnion function from adjoining shapes; the 
> resulting shapes are multipolygon with internal divisions, and overlay gives 
> an error with this kind of shapes.
> Unfortunately, I did not find a command which removes the internal divisions 
> (of course a workaround is to export it and edit it, but I would like to find 
> a cleaner solution).
> All the best.
> 
> 
> Alle 16:05, lunedì 17 ottobre 2005, Emilia Venturato ha probabilmente scritto:
> > Hi all,
> >
> > I'm trying to extract from a postgis table (the_geom of table1: 25.000
> > records) all the id of that records wich overlay (also partially) with a
> > study_area (the_geom of table2).
> > I try:
> >
> > select a.id, disjoint (a.the_geom, b.the_geom) from table1 a, table2 b
> > where disjoint (a.the_geom, b.the_geom) is false;
> > select a.id, overlay (a.the_geom, b.the_geom) from table1 a, table2 b where
> > overlay (a.the_geom, b.the_geom) is true;
> >
> > In both queries, I had an error:
> > ERROR:  GEOS disjoin() threw an error!
> > ERROR:  GEOS overlay() threw an error!
> >
> > I tryed with a subsample (900 records) and the select worked.
> > Have you same suggestion? Could it be a problem in the (too large?) number
> > of records?
> > Thank you in advance.
> > Lia
> 
> -- 
> (Emi)Lia Venturato
> venturato at faunalia.it    venturato at jabber.org    www.faunalia.it
> Piazza Garibaldi 4 56025 Pontedera (PI)  Italy
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