Bugs item #3607970, was opened at 2013-03-13 21:12 Message generated for change (Comment added) made by michaudm You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=679906&aid=3607970&group_id=118054
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: General / Other Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Sean (bigrodent) Assigned to: Nobody/Anonymous (nobody) Summary: Generalization will remove full polygons for high tolerance Initial Comment: Take for instance a US Zip and set it to .01 or even as low as .0001 and you will end up with less polygons than the original file. You will actually remove full zip codes. As you turn the tolerance down they gradually appear back. Upon physical inspection of the shapefile it is clear that it is the smallest zips in the file that get stripped first. Other opensource tools have this issue as well. ---------------------------------------------------------------------- >Comment By: michael michaud (michaudm) Date: 2013-03-14 00:51 Message: Jukka is right about the difference between DouglasPeuckerSimplifier and TopologyPreservingSimplifier. However, I don't remember I have seen geometries disappearing with DouglasPeuckerSimplifier. On the other hand, I just check our Simplify Polygon Coverage plugin and found a flaw which could explain that small polygons disappear (just added some comments in the code of SimplifyPolygonCoveragePlugIn). I've no patch yet and I'll try to find a solution with the help of Stefan. ---------------------------------------------------------------------- Comment By: Jukka Rahkonen (jratike80) Date: 2013-03-13 22:27 Message: I can confirm that this happens with Simplify Polygon Coverage and OJ snapshot r3322. Douglas Peucler simplification is not guaranteed to preserve the number of polygons http://tsusiatsoftware.net/jts/javadoc/com/vividsolutions/jts/simplify/DouglasPeuckerSimplifier.html There are another algorithms which keep all the polygons like http://tsusiatsoftware.net/jts/javadoc/com/vividsolutions/jts/simplify/TopologyPreservingSimplifier.html I am not sure if our Simplify Polygon Coverage is supposed to preserve the topology or not and if this is a bug or a missing feature. I used Spatialite and SimplifyPreserveTopology function for my data with good result. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=679906&aid=3607970&group_id=118054 ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_mar _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
