[postgis-users] Topology Issue Reported by Query but Not Identified with ST_IsValid

Michael Treglia mtreglia at gmail.com
Fri May 27 05:47:50 PDT 2016


Ah, I see - Thanks Regina! I was wondering if it was something like that,
as the area identified it with the issue definitely had lots of adjacencies.

I'll give that a try and report back,
Best,
Mike


On Fri, May 27, 2016 at 12:47 AM, Regina Obe <lr at pcorp.us> wrote:

> Try replacing your ST_Collect call with ST_Union.
>
>
>
> ST_Collect when used with polygons will create invalid multipolygons since
> it just collects them up, and if they are adjacent, it's not a valid
> multipolygon.
>
>
>
> Hope that helps,
>
> Regina
>
> http://www.postgis.us
>
> http://postgis.net
>
>
>
>
>
>
>
> *From:* postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] *On
> Behalf Of *Michael Treglia
> *Sent:* Thursday, May 26, 2016 10:34 PM
> *To:* PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> *Subject:* [postgis-users] Topology Issue Reported by Query but Not
> Identified with ST_IsValid
>
>
>
> Hi All,
>
>
>
> I was running a query involving ST_Difference between two multipolygon
> layers, and a while in, it threw this message:
>
> ERROR: GEOSDifference: TopologyException: side location conflict at
> 919670.1768945494 140665.82566365649
>
>
>
> However, I previously ran ST_MakeValid, and ST_IsValid doesn't report any
> objects with problems. Is there something I'm missing, or something else I
> need to check? (Apologies is this is just a naive question - still learning
> my way around PostGIS).
>
>
>
> And in case it helps, here's my SQL:
>
>
>
> CREATE TABLE SI_Unclaimed AS
>
> SELECT gid, COALESCE(ST_Difference(geom_2263, (SELECT
> ST_Collect(b.geom_2263)
>
>                                          FROM citywide_basedata.parcels15 b
>
>                                          WHERE ST_Intersects(a.geom_2263,
> b.geom_2263)
>
>                                          )), a.geom_2263)
>
> FROM citywide_basedata.boroughs_nowater a where boroname like 'Staten
> Island';
>
>
>
> Thanks!
>
> Mike
>
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