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Mapforge renders multipolygons with more than one "outer" way incorrectly #290

mapsforge opened this issue Nov 6, 2014 · 4 comments


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From on April 11, 2012 13:33:26

Mapforge renders multipolygons with more than one "outer" way incorrectly.

Example relation: (outer ways in this relation are in correct order and even follow "old-days" rule - ways go in clockwise direction)

Note that OSM has a hardcoded limit that a way cannot contain more than 2000 nodes, therefore most large forests are marked with more than one outer way.

P.S. Mapnik, osmarender, mkgmap are handling this type of multipolygon correctly, maybe code/routines could be re-used? (mkgmap is a java app)

Tested with latest stable release v0.3.0

Attachment: vilnius-draw-error.png

Original issue:

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From on April 13, 2012 20:12:11

I was just looking at this and there has been some editing on the relevant items recently, including the deletion of way inside the reiation: See e.g. I am not sure what is really happening there, but two people seem to be fighting something out over that relation, which might not be helpful investigating this case.

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From on April 14, 2012 02:57:17

There was a bit of misunderstanding there, but just refer to latest version of map for debugging - it has been settled on that.

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From on April 22, 2012 20:49:52

I have investigated this issue and the problem was, as I thought previously, that the OSM data was incorrect.

Some of the renderers are more forgiving than others and (in some ways unfortunately) the main OSM site renders incorrect data 'correctly', with the result that people do not realize that they have done something wrong.

Anyway, the problem here was that for the river multipolygon the two ways that made up the outer part of relation #968968 were tagged as waterway=riverbank. However, the OSM documentation is clear that this is to be used only for polygons. JOSM actually flagged a validation violation.

To investigate this, I ran the map writer just with the data for relation 968968, then fixed the data and ran it again. Screenshots and osm data files are attached if someone wants to repeat this.

I have committed the fix of the data to OSM, for anyone getting the new data from a planet or so, you might have to wait for a day or two for it to filter through.

I will test the map building again, once it has arrived in the Geofabrik copies, but I hope this is solved.

Attachment: vilnius-1.osm vilnius-1.png vilnius-2.osm vilnius-2.png

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From on April 23, 2012 14:18:49

Thanks a lot for investigating this issue. Based on your findings i consider it as solved.

Status: Done

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