[postgis-users] Problems with GeomUnion

[Martin Davis]

> 1) What tool did you use to find that?

JUMP (http://www.jump-project.org/project.php?PID=JUMP&SID=OVER)  has a
Validation tool which can find geometry validation errors.  You can just
cut and paste WKT into layers in JUMP, and then validate them.  JUMP
uses JTS, which is the Java API which the GEOS engine in PostGIS is
based on.

> 2) Is there a way to test shapes for validity in PostGIS?  Like an 
> isvalid() function?

Yep - but I'm no PostGIS expert.  Others on the list can help with this,
I'm sure.

Martin Davis, Senior Technical Architect
Vivid Solutions Inc.      www.vividsolutions.com
Suite #1A-2328 Government Street Victoria, B.C. V8T 5G5
Phone: (250) 385 6040 - Local 308 Fax: (250) 385 6046


> -----Original Message-----
> From: Bill Binko [mailto:bill at binko.net] 
> Sent: April 7, 2005 4:25 PM
> To: PostGIS Users Discussion
> Subject: RE: [postgis-users] Problems with GeomUnion
> 
> 
> On Thu, 7 Apr 2005, Martin Davis wrote:
> 
> > The large polygon is invalid.  It has a self-intersection 
> in the lower 
> > left corner at the boundary with the other polygon.  One of 
> the input 
> > polygons which formed it must be invalid.
> > 
> > (See attached screenshot)
> 
> Thanks for the quick response!  A couple of questions:
> 
> 1) What tool did you use to find that?
> 2) Is there a way to test shapes for validity in PostGIS?  Like an 
> isvalid() function?
> 
> Thanks
> Bill
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