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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>From: Alexandre Silva <amsilva@infoportugal.impresa.pt>Sent: Monday, November 23, 2020 2:38 PMTo: PostGIS Users Discussion <postgis-users@lists.osgeo.org>;
Lars Aksel Opsahl <Lars.Opsahl@nibio.no>Subject: Re: [postgis-users] Topology creation performance</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>On 23/11/20 07:39, Lars Aksel Opsahl wrote:</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>Hi and thanks for your input,</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>I saw your foss4g presentation and your approach was one that I was</span></div>
<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>considering use, but I hadn't find the source code yet outside of the</span></div>
<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>slides.</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>Do the repo approach have the same ruleset as the presentation?</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Hi</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Yes pretty much but , but I have the made merging of cells a bit more complicated.</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">I also tried to cut off crossing part with a tolerance for lines that was crossing cell borders and glue them in later but that just made the code more
complex and less robust .</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">I mostly only focus on the edges because Sandro's Topology code makes sure that all faces also are available if I manage add all edges correctly. From
the faces I then generate the surfaces (polygons) when needed. </span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>I have</span></div>
<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>the need of processing only cells when there is no line falling outside</span></div>
<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>that cell or the ordering may not be respected, so the cell merging is</span></div>
<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>also a point that I have to ensure.</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">This I did not understand because the order of adding edges should not have any effect on the result, related to faces generated.</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">About big polygons, we have polygons 295834 points and 5042 holes and Postgis Topology seems to handles it OK, with breaking them up in to smaller parts.</span><br>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>Thanks,</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">>Alexandre Silva</span></div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">My experience is that Postgis Topology is very good tool for instance to :<br>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">(Because we have a single line between polygons that intersects and not two different lines and objects as in simple feature)
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<li><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Ensure that your data are spatially consistent when updated</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"></span></li><li><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Remove overlap and gap from simple feature dataset's</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"></span></li><li><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Line smoothing for instance when converting pixel data to vector a kind of
</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">generalization</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> .</span><br>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">With help from Sandro, Nibio has been working projects
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<li><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"><a href="https://github.com/NibioOpenSource/pgtopo_update_sql" id="LPlnk">https://github.com/NibioOpenSource/pgtopo_update_sql</a> :
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<li><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">make simple clients for updating of Postgis Topology</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"></span></li></ul>
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<li><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"><a href="https://github.com/larsop/resolve-overlap-and-gap" id="LPlnk765740">https://github.com/larsop/resolve-overlap-and-gap</a></span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"></span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
: <br>
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<li><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">to clean up in overlap gaps from Simple Feature dataset's and return a new clean Simple Feature datset's</span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"></span></li><li><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">to convert simple feature data (surface only or both line and surface with attributes)
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">You mention funding of Postgis Topology, I would love to see more funding of Postgis Topology because without Postgis we would not have been able handle
problems caused by simple feature in such an efficient way.</span></div>
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<span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Lars</span>
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