"postgis_full_version"
"POSTGIS=""1.4.0"" GEOS=""3.1.1-CAPI-1.6.0"" PROJ=""Rel. 4.6.1, 21 August
2008""
USE_STATS"
________________________________
From: Kevin Neufeld <[email protected]>
To: PostGIS Users Discussion <[email protected]>
Sent: Wed, September 15, 2010 4:46:37 PM
Subject: Re: [postgis-users] unioning a buffer - bug?
Hi Lee,
Unfortunately, I can't duplicate your error. I can
st_union(st_buffer(geom,
0.1)) no problem ...
POLYGON ((
586801.773149238 4951692.01936019,
586801.773148314 4951692.01935961,
586773.455669237 4951674.0093102,
....
What version of GEOS are you running? As I've said, it works fine for me
running 3.2.2. Perhaps you need to upgrade?
Cheers,
Kevin
On 9/15/2010 12:09 PM, Lee wrote:
okay so I plotted those points that were in the topology exception
error, and narrowed it down to two adjacent polygons. So now I have:
>select st_union(st_buffer(the_geom,0.1)) from
>base.current_assessment_parcel where gid in (36,37)
>(returns the topology exception)
>
>Checking out those two parcels, they seem legit in qgis / arcview. (no
>weird nodes that I can see).
>
>
>Attached is the output from the following query: select gid,
>st_asewkt(the_geom) from base.current_assessment_parcel where gid in
>(36,37)
>
>I'm relatively newbie to postgis, so can't see what might be causing
>this, if someone could look at this for me?
>
>
unfortunately, I am on vacation starting tonight, and won't be
available
to provide further details. If the answer is "your polygons are just
messed up" then so be it. These are from someone elses shapefile. Just
want to help if this is indeed a bug.
>
>Thanks for your help Kevin.
>Lee.
>
>
>
>
>
>
________________________________
From: Kevin Neufeld <[email protected]>
>To: PostGIS Users Discussion
><[email protected]>
>Sent: Tue, September 14, 2010 10:49:25 PM
>Subject: Re: [postgis-users] unioning a buffer - bug?
>
>Interesting. Something sure sounds amiss. Are the results null?
>Is there anything usual occurring at the TopologyException
>
>location? Is your dataset large? Can you winnow it down to the
>few
>polygons that might be causing the problem (this may be just the
>polygons around the TopologyException location)? If
>so,
>you could paste the representation of the geometries
>in
>PasteBin or something so we can help you isolate the
>problem.
>
>Also, what version of GEOS do you have installed?
>SELECT PostGIS_Full_Version();
>
>Cheers,
>Kevin
>
>On 9/14/2010 6:03 AM, Lee wrote:
>Hi Kevin,
>>
>>I assumed I have no results because when I load one of the
>>working queries as a view (eg. select
>>st_buffer(the_geom,0.1))
>>in QGIS, or in ArcGIS, I see all my results as I would
>>expect,
>>but when I modify the query to
>>st_union(st_buffer()), all my parcels disappear and I have a
>>
>>blank canvas.
>>
>>Also, with st_isvalid(st_union(st_buffer(the_geom,0.1)))
>>returning null (neither t nor f) I guess I just assumed.
>>Anyways, results for your suggestions are
>>inline, below.
>>
>>
>>
>>Thanks for your help. Any further ideas?
>>
>>Lee.
>>
>>
________________________________
From: Kevin Neufeld <[email protected]>
>>To: [email protected]
>>Sent: Tue, September 14, 2010 12:12:46 AM
>>Subject: Re: [postgis-users] unioning a buffer - bug?
>>
>>How are you determining you have no results?
>>
>>Try:
>>CREATE TABLE results AS
>>SELECT st_union(st_buffer(the_geom,0.1)) as the_geom
>>FROM base.current_assessment_parcel;
>>
>>NOTICE: TopologyException: found non-noded
>>intersection
>>between 586714 4.95189e+006, 586714 4.95189e+006 and
>>586714 4.95189e+006, 586739
>>4.9519e+006 586714 4.95189e+006
>>Query returned successfully with no result in 1078 ms.
>>
>>
>>
>>SELECT count(*) FROM results;
>>
>>1
>>
>>SELECT ST_Summary(the_geom) FROM results;
>>
>>This returns blank.
>>
>>
>>(snip)
>>
>>-- Kevin
>>
>>On 9/13/2010 7:07 AM, Lee wrote:
>>So after some googling I see
>>
>>similar problems, but no solutions posted.
>>>
>>>I am trying to union a buffer, but
>>>
>>>the query is returning no results. Here is
>>>ultimately what I would like to achieve:
>>>
>>>select st_union(st_buffer(the_geom,0.1)) as
>>>the_geom
>>>from base.current_assessment_parcel
>>>
>>>Here are some
>>>troubleshooting steps I have taken to try narrow
>>>it
>>>down:
>>>
>>>select st_isvalid(the_geom)
>>>
>>>a from base.current_assessment_parcel group by a
>>>TRUE
>>>
>>>select st_isvalid(st_buffer(the_geom,0.1))
>>>
>>>a from base.current_assessment_parcel group by a
>>>TRUE
>>>
>>>select st_isvalid(st_union(the_geom))
>>>
>>>from base.current_assessment_parcel
>>>TRUE
>>>
>>>select
>>>st_isvalid(st_union(st_buffer(the_geom,0.1)))
>>>from base.current_assessment_parcel
>>>NOTICE: TopologyException:
>>>
>>>found non-noded intersection between 586714
>>>4.95189e+006, 586714 4.95189e+006 and 586714
>>>4.95189e+006, 586739 4.9519e+006 586714
>>>4.95189e+006
>>>Total query runtime: 859
>>ms.
>>>1 row retrieved.
>>>(returns blank
record)
>>>
>>>
>>> And just for fun
>>>select
>>>st_isvalid(st_buffer(st_union(the_geom),0.1))
>>>a from base.current_assessment_parcel
>>>TRUE
>>>
>>>
>>>I guess my next
>>>step
>>>would be to try the snap to grid functions,
>>>but
>>>the first query above should work, shouldn't
>>>it?
>>>
>>>Any help appreciated. Thanks.
>>>Lee
>>>
>>> _______________________________________________ postgis-users mailing list
>>>[email protected]
>>>http://postgis.refractions.net/mailman/listinfo/postgis-users
>>>
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>>
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