On Tuesday 29 August 2017, Jochen Topf wrote: > We have completed the 7-months effort to switch away from old-style > multipolygons and fix a lot of broken (multi)polygons. More about > this on my blog: > > https://blog.jochentopf.com/2017-08-28-polygon-fixing-effort-conclude >d.html
First of all congratulations to what was achieved, i.e. a fairly massive reduction in the number of errors. The sad news however seems to be that given the current circumstances the number of errors will likely be back to near the pre-cleanup levels in 2-3 years for many types of errors. From my point of view this is because in contrast to the old style multipolygons where * the problem was fully eliminated in the data * the most important data user (the standard map) was changed to not interpret old style MPs any more after that * the major editors had already ceased to generate old style MPs long ago the circumstances that lead to the large number of broken multipolygons are essentially unchanged. We certainly got rid of a number of errors from bad imports and can hope that future imports will be better in that regard but the problem that mappers introduce this kind of error in manual mapping and don't realize they are making an error is unchanged. Of the points above both completely eliminating MP geometry errors and changing the editors not to upload broken geometries are things that are very hard to accomplish. This leaves the third point and therefore my question: Would the number of visible problems in the map due to dropping broken geometries now, after the fixing effort, be low enough so this change could be made to the main map to give mappers a better feedback about broken geometries? If the answer to this question is yes (or almost yes) we should not wait too long with making this step because once the number of errors has risen again this will again become increasingly problematic. And if this is not considered a practicable step there will of course be increasing need for libosmium to be able to fix these errors, at least the self intersections. ;-) -- Christoph Hormann http://www.imagico.de/ _______________________________________________ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
