[geos-devel] RE: GEOS errors from PostGIS

[Martin Davis]

FWIW, I ran this data through JTS 1.11 using both union(geom, geom) and 
union(geom), and both operations completed without errors.

Not sure what this says about the GEOS issue - other than more debugging 
required...!

On 1/20/2011 3:31 PM, James.Sewell at lisasoft.com wrote:
> 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
>
>
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>
> -----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
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