[OSM-talk] Rendering issues with Carto 4.0

Jochen Topf jochen at remote.org
Tue Jun 20 09:24:36 UTC 2017


In the last days the OpenStreetMap Carto Style 4.0 is being deployed on
the OSMF tile servers. This new version of the style doesn't take old-style
multipolygons (where the tags are on the outer ways instead of on the
relation) into account any more. In a huge effort in the last months we
have removed old-style multipolygons from the OSM database completely,
so this is a good step!

Unfortunately nobody really realized that as a side-effect of the update
to Carto 4.0 many multipolygon relations would appear wrong on the map.
This is the case for multipolygon relations that have the same tags on
the relation as well as on (some of the) outer or inner ways. This is
*wrong* tagging, and needs to be fixed. Note that this always was wrong
tagging, even before we deprecated old-style multipolygons, but the way
the software worked with old-style multipolygons, this problem was not
visible on the map.

Here is an example: http://www.openstreetmap.org/relation/1330741 . As
you can see (unless somebody fixes this :-) the clearing in the forest
that should just have grass, also has tree symbols on it. In many other
cases it is not this obvious, there are just islands in a river missing
or so.

There are about 50,000 cases like this, forests, waterways, all sorts of
areas. Worst offenders are about 15,000 relations from imports in Canada
and 8,000 relations from imports in New Zealand.

Please help fixing these. As part of the "area fixing effort" I have
started to create Maproulette challenges for these. Go to
http://area.jochentopf.com/fixing.html for more information and read
the detailed news about this effort at
https://github.com/osmlab/fixing-polygons-in-osm/issues/15 .

Jochen Topf  jochen at remote.org  https://www.jochentopf.com/  +49-351-31778688

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