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<p>Hi Strk,</p>
<p>Thank you for these hints.</p>
<p>It will help me to get started - also combined with your blog entries on the topic!</p>
<p>Andreas</p>
<p>On 2016-07-01 10:29, Sandro Santilli wrote:</p>
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<div class="pre" style="margin: 0; padding: 0; font-family: monospace">On Thu, Jun 30, 2016 at 11:25:22AM +0200, Neumann, Andreas wrote:<br /><br />
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">Is there a method in Postgis to create a Topology, eliminating double<br /> borders from the original CurvePolygons and attaching left and right<br /> attributes from the original polygons? I came across the Postgis<br /> topology module. Is this the recommended way of achieving my above goal?</blockquote>
<br /> I'd say YES -- the standard ISO Topology Model involves having<br /> "left face" and "right face" information for each edge.<br /><br />
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">Unfortunately, there are only few ressources or examples around Postgis<br /> topology and from the first glimpse it looks a bit complicated to use.</blockquote>
<br /> The simplest path to try it would something like this:<br /><br /> -- Create the topology<br /> SELECT CreateTopology('topo', find_srid('public','mytable','geom'));<br /><br /> -- Populate the topology layer<br /> SELECT ST_CreateTopoGeo('topo', (<br /> SELECT ST_Collect(geom) FROM mytable<br /> ) );<br /><br /> Then fire up qgis, select the 'topo' schema with the DB Manager<br /> and from the menu select Schema->TopologyViewer.<br /><br />
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">It also looks like it can't handle CurvePolygons as input - right? I<br /> would have to coerce first to POLYGON geometries - right? It is ok for<br /> me if the circular arcs are segmentized, as this data is not for<br /> editing/analysis, but only for symbology purposes.</blockquote>
<br /> Confirmed, yo'll have to convert to POLYGON first.<br /><br />
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">If you have any hints or examples, please let me know!</blockquote>
<br /> I guess you did read these already ?<br /><a href="https://strk.kbt.io/blog/tag/topology/">https://strk.kbt.io/blog/tag/topology/</a><br /><br /> --strk;</div>
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