<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Does Postgis ST_SimplifyPreserveTopology() work for you?<br><br><a href="http://postgis.org/docs/ST_SimplifyPreserveTopology.html">http://postgis.org/docs/ST_SimplifyPreserveTopology.html</a><br><br>Cheers,<br><br>&nbsp; Brent Wood<br><br><br><br>--- On <b>Tue, 2/21/12, Arnd Wippermann <i>&lt;arnd.wippermann@web.de&gt;</i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Arnd Wippermann &lt;arnd.wippermann@web.de&gt;<br>Subject: [gdal-dev] Simplify a polygon topology doesn't preserve the topology<br>To: gdal-dev@lists.osgeo.org<br>Date: Tuesday, February 21, 2012, 10:36 AM<br><br><div class="plainMail">Hi,<br><br>I try to simplify a polygon topology (GDAL 1.9.0, released 2011/12/29).<br><br><br>SET INPUT="top1_bene.gml"<br><br>SET OUTPUT_01="top1_bene_sim_01.gml"<br>SET
 OUTPUT_005="top1_bene_sim_005.gml"<br>SET OUTPUT_001="top1_bene_sim_001.gml"<br><br>"%prgpfad%\ogr2ogr" -f "GML" %OUTPUT_01%&nbsp; %INPUT% -simplify 0.1<br>"%prgpfad%\ogr2ogr" -f "GML" %OUTPUT_005% %INPUT% -simplify 0.05<br>"%prgpfad%\ogr2ogr" -f "GML" %OUTPUT_001% %INPUT% -simplify 0.01<br><br><br>but preserving the topology doesn't work for tolerances above a treshold.<br><br>I get a correct result for a tolerance of 0.01, but for 0.05 and 0.1<br>the results are only in parts correct.<br><br>see:<br><a href="http://gis.ibbeck.de/OLClient/OLClient.asp?WMC=/ginfo/tests/ogr/simplify/Sim" target="_blank">http://gis.ibbeck.de/OLClient/OLClient.asp?WMC=/ginfo/tests/ogr/simplify/Sim</a><br>plify_bene_ogr.wmc.xml<br><br>I have it also tried with a polygon topology of the us states and the result<br>wasn't great.<br><br>(I get similar results using postGis ST_Simplify.)<br><br>Apart the tolerance are there other options to consider or is it a bug?<br><br>The
 polygon topology consists of two polygons and the shared border have<br>identical vertices.<br><br>Arnd<br><br>_______________________________________________<br>gdal-dev mailing list<br><a ymailto="mailto:gdal-dev@lists.osgeo.org" href="/mc/compose?to=gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a><br><a href="http://lists.osgeo.org/mailman/listinfo/gdal-dev" target="_blank">http://lists.osgeo.org/mailman/listinfo/gdal-dev</a><br></div></blockquote></td></tr></table>