[OSM-talk] [OSM-dev] Detect and remove sharp angle/spiky configurations on buildings

[Pierre Béland]

 oups, Resending previous incomplete message

Sandor, 
 you are looking only at spikes. My algorithm presented in recent threads on the talk list about Building Geometries detection will also detect regular geometries that have any irregular edge ( a difference of more then 2 degrees ).  It cannot distinguish valid irregular geometries, but they are in general a small numbers, and most flagged buildings correspond to imprecise building traces.

regular polygons-   90, 90, 90, 90
-   90, 270, 90, 90, 90, 90
-  120 * 6 (hexagon)-  135 * 8 (octagon)

refhttps://lists.openstreetmap.org/pipermail/talk/2018-August/081274.htmlhttps://lists.openstreetmap.org/pipermail/talk/2018-September/081392.html 
 
Pierre 
 

  

Pierre 
 

    Le jeudi 18 octobre 2018 09 h 15 min 53 s HAE, SandorS <sandors39 at gmail.com> a écrit :  
 
 
Some days ago there was a question on an OSM forum whether such algorithm exists and used by some of the OSM users. Honestly I even did not know that such an issue exists and probably I am not alone. The reason to that is either that the spiky configurations are hardly visible in maps or that robust users handle them as a special case when process tiny outgrowths in their data generalisation programs. A closer look at the issue has shown that the issue is real and rather general. Spiky configurations exist on most of the area borders, roads, roundabouts and so on, there is a huge number of them and almost all are errors. To provide strong arguments about the former statement I have made an algorithm, a simplified version of the tiny outgrowths detection and removal, and applied the corresponding program to the OSM UK buildings. The algorithm on a certain abstraction level, its use and the processing results are described in details in an article here https://drive.google.com/open?id=1MaLdnSnc454xKjn3eL95vDQKeoIW8zGU . There are around 120K spiky buildings in OSM and out of these 2834 in the UK. In addition, the paper presents many examples how the spiky buildings look before and after the correction. Also, the paper contains links to the output data of the demo/test processing and how these could be used for visual analyses. So, if interested, enjoy the paper.

Regards, Sandor.

  

  

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