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List: postgis-users
Subject: Re: [postgis-users] TopologyException: side location conflict
From: Stefan Zweig <stefanzweig1881 () web ! de>
Date: 2007-04-24 21:21:58
Message-ID: 56792332 () web ! de
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hi martin,
thank you for your advice with using buffer(0) i am going to give that i try \
tomorrow.
i have had i look on the TopologyPreservingSimplifier but the doc (unfortunately i \
could not find the code) only says that it 'preserves the number of touches' \
(whatever that means, i guess that the number of touching points/nodes of a set of \
geometries within a topological network is meant).
but this would not give the functionality that is needed to prevent from getting \
"NOTICE: TopologyException: side location conflict (-81.0351,26.6027,26.6027) ERROR: \
GEOS within() threw an error! " using geos spatial analyzing functions on simplified \
geometries, which are not explicitely part of a topological network such as simple \
polygons. don't you think so?
regards. stefan
Martin Davis schrieb:
> Ah, right - that makes sense. Ordinary Douglas-Peucker simplification is not \
> guaranteed to maintain topology.
> JTS has a TopologyPreservingSimplifier which is safe to use. This is in GEOS, but \
> is apparently not exposed in PostGIS, however.
> As an interim measure, you might try using buffer(0), which should have the effect \
> of cleaning up the invalid geometry.
> Stefan Zweig wrote:
> > Hi Martin,
> >
> > this is a geometry-example which causes the error. (already the result of \
> > simplify(p."the_geom",0.001))
> > "SRID=4326;MULTIPOLYGON(((12.580188 51.373967,12.562256 51.393057,12.522384 \
> > 51.405868,12.509405 51.422205,12.493471 51.421644,12.48965 51.428585,12.516928 \
> > 51.447914,12.508014 51.473221,12.51922 51.492546,12.509222 51.492563,12.498616 \
> > 51.525579,12.483908 51.532504,12.5090463 51.5359336,12.510126 \
> > 51.542813,12.5197436 51.5336497,12.521997 51.543612,12.533731 51.542285,12.537291 \
> > 51.554611,12.561063 51.561843,12.565748 51.576295,12.59227 51.574819,12.606697 \
> > 51.586819,12.62031 51.574803,12.643358 51.570059,12.638377 51.562592,12.653986 \
> > 51.555776,12.679631 51.567556,12.699531 51.552931,12.753434 51.567096,12.813991 \
> > 51.565712,12.816714 51.559281,12.824765 51.563208,12.825679 51.546586,12.86806 \
> > 51.551449,12.877856 51.545186,12.860509 51.545619,12.915288 51.537334,12.8992658 \
> > 51.5202663,12.934356 51.501062,12.924406 51.478989,12.9096214 \
> > 51.4779279,12.8932373 51.5065071,12.9001306 51.4729784,12.835224 \
> > 51.46272,12.833034 51.450177,12.789232 51.468401,12.7522 51.453984,12.720131 \
> > 51.45454,12.712384 51.445902,12.664772 51.449811,12.645697 51.43669,12.6469931 \
> > 51.4274848,12.65846 51.425221,12.645563 51.417605,12.648839 51.406172,12.622621 \
> > 51.408846,12.610952 51.382359,12.590127 51.383687,12.580188 \
> > 51.373967)),((12.9265896 51.5226495,12.907823 51.5192242,12.906139 \
> > 51.528584,12.9265896 51.5226495)),((12.9088754 51.5469124,12.922428 \
> > 51.543913,12.897451 51.542675,12.896428 51.548283,12.9088754 51.5469124)))"
> > meanwhile i have found out that the geometry is not valid because it has \
> > self-intersections which causes geos-analyzing functions to abort. if i do \
> > exclude invalid geometries from my query with isvalid() the query works fine. but \
> > this is only a workaround. it would be nice if either the simplification would \
> > not return self-intersecting geometries or geos could better deal with them e.g. \
> > not interrupt the whole query.
> > is there maybe another workaround?
> >
> > regards.
> >
> >
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: PostGIS Users Discussion <postgis-users@postgis.refractions.net>
> > > Gesendet: 23.04.07 18:33:32
> > > An: PostGIS Users Discussion <postgis-users@postgis.refractions.net>
> > > Betreff: Re: [postgis-users] TopologyException: side location conflict
> > >
> >
> >
> >
> > > Can you post two geometries which cause the error?
> > >
> > > Both WKT and WKB would be nice.
> > >
> > > Stefan Zweig wrote:
> > >
> > > > hi @ all,
> > > >
> > > > i have following problem with the postgis WITHIN method:
> > > >
> > > > i am trying to check whether some polygons from one layer/table are within a \
> > > > polygon from another layer/table and i am doing this with this sql command:
> > > > SELECT p."POSTCODE"
> > > > FROM _countys b AS b, postcodes AS p
> > > > WHERE b."NAME"='florida' AND p."the_geom" @ b."the_geom" = true
> > > > AND WITHIN(p."the_geom", b."the_geom") = true
> > > > ;
> > > >
> > > > this works fine but takes i while to be procedured. so i wanted to make the \
> > > > within check faster by simplifying the source geometries (EPSG: 4326):
> > > >
> > > > SELECT p."POSTCODE"
> > > > FROM _countys b AS b, postcodes AS p
> > > > WHERE b."NAME"='florida' AND p."the_geom" @ b."the_geom" = true
> > > > AND WITHIN(simplify(p."the_geom",0.001), simplify(b."the_geom",0.001)) = true
> > > > ;
> > > >
> > > > but then i get the following error:
> > > >
> > > > NOTICE: TopologyException: side location conflict (-81.0351,26.6027,26.6027)
> > > >
> > > > ERROR: GEOS within() threw an error!
> > > > SQL Status:XX000
> > > >
> > > > i am wondering why the within operator does not work with simplified \
> > > > coordinates / geometries.
> > > > btw.: i does not seem that this error occurs with any within/simplify usage, \
> > > > only in some cases.
> > > > i appreciate any help.
> > > >
> > > > stefan
> > > > _______________________________________________________________
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> > > >
> > > >
> > > --
> > > Martin Davis
> > > Senior Technical Architect
> > > Refractions Research, Inc.
> > > (250) 383-3022
> > >
> > > _______________________________________________
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> > > postgis-users@postgis.refractions.net
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> > >
> > >
> >
> >
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>
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