[OSM-talk] Multipolygon fixing effort done
Jochen Topf
jochen at remote.org
Tue Aug 29 13:35:46 UTC 2017
On Tue, Aug 29, 2017 at 12:10:47PM +0200, Christoph Hormann wrote:
> Date: Tue, 29 Aug 2017 12:10:47 +0200
> From: Christoph Hormann <osm at imagico.de>
> To: talk at openstreetmap.org
> Subject: Re: [OSM-talk] Multipolygon fixing effort done
>
> 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.
What has changed is that now without the complication of the old-style
MPs it is easier to check for correctness of the data in editors and
other tools. I hope that especially editor developers are looking at
this problem more closely to identify common problems that can be fixed
by better UI or better checking on their code.
> 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?
Osm2pgsql is switching to the libosmium MP code which is more strict
than the older code before. As far as I know the code is finished and
should be in the next osm2pgsql version.
Jochen
--
Jochen Topf jochen at remote.org https://www.jochentopf.com/ +49-351-31778688
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