[geos-devel] RE: GEOS errors from PostGIS

[James.Sewell at lisasoft.com]

Right,

Once again thanks for the help on this.

Attached is a zip with the two geometries that I am having problems unioning (2.7mb I'll up to an FTP if it doesn't get through), when testing I have them both in a table called alw as separate rows. I realise that the linework is very dirty, but it is what we have to work with in this case.

The following commands will cause errors. If I don't include the snaptogrid there will not be an error in *this* case, but if I were to run the whole process with no snap there would be an error at some stage.

Any help appreciated! I am working on getting a smaller dataset which exhibits the problem.

--

CREATE TABLE alwunionxx AS
	SELECT 
		st_union(st_collect(st_snaptogrid(the_geom,10E-8)), ST_SetSRID('LINESTRINGEMPTY', 4283)) 
	AS the_geom 
	FROM alw;

NOTICE:  TopologyException: found non-noded intersection between LINESTRING (146.593 -37.2263, 146.593 -37.2263) and LINESTRING (146.593 -37.2263, 146.593 -37.2263) at 146.593 -37.2263
ERROR:  GEOS union() threw an error!


CREATE TABLE alwunionxx AS
	SELECT 
		st_union(st_snaptogrid(the_geom,10E-8)) 
	AS the_geom    
	FROM alw;

NOTICE:  TopologyException: found non-noded intersection between LINESTRING (146.593 -37.2263, 146.593 -37.2263) and LINESTRING (146.593 -37.2263, 146.593 -37.2263) at 146.593 -37.2263
ERROR:  GEOS union() threw an error!

--

Cheers,
James Sewell 
Developer 
LISAsoft 

Ph: +61 3 8680 3250 Fax: +61 3 8680 3299 
Level 9, 601 Bourke St, Melbourne Vic 3000


LISAsoft is part of the A2end Group of Companies
http://www.ardec.com.au
http://www.lisasoft.com
http://www.terrapages.com

-----Original Message-----
From: geos-devel-bounces at lists.osgeo.org [mailto:geos-devel-bounces at lists.osgeo.org] On Behalf Of strk
Sent: Tuesday, 18 January 2011 2:48 AM
To: GEOS Development List
Subject: Re: [geos-devel] RE: GEOS errors from PostGIS

On Mon, Jan 17, 2011 at 11:05:42AM +1030, James.Sewell at lisasoft.com wrote:
> The latest daily doesn't help the problem so I've reverted to 3.2.2 and performed some more testing.
> 
> I have a dataset where:
> 
> ST_Union(the_geom, ST_SetSRID('LINESTRING EMPTY', 4283))
> 
> Fails, yet
> 
> ST_Union(the_geom).
> 
> Works. There are other datasets which fail on both versions, and I have no doubt I can find one which works in the reverse manner.

The latter uses CascadedUnion (the one UnaryUnion uses too).
The former uses normal union (non-cascaded).

--strk;

  ()   Free GIS & Flash consultant/developer
  /\   http://strk.keybit.net/services.html
_______________________________________________
geos-devel mailing list
geos-devel at lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/geos-devel
-------------- next part --------------
A non-text attachment was scrubbed...
Name: errors.zip
Type: application/x-zip-compressed
Size: 2777981 bytes
Desc: errors.zip
Url : http://lists.osgeo.org/pipermail/geos-devel/attachments/20110121/f87c2be4/errors-0001.bin