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Look at the two consequtive zoom levels

http://www.openstreetmap.org/?lat=47.792&lon=-85.794&zoom=9&layers=M

and

http://www.openstreetmap.org/?lat=47.791&lon=-85.793&zoom=10&layers=M

In the level 10 the green (assume forest) on some islans disapear but not on the other land areas. Is there a special reason for that?

asked 27 Feb '13, 22:06

sanser's gravatar image

sanser
665333653
accept rate: 5%

edited 28 Feb '13, 10:16

gormo's gravatar image

gormo
2.9k32660


This is an issue in the data, not in the rendering.

Problem : this island is modelized two times.

First time with a single closed way (polygon) tagged with "natural=land":
http://www.openstreetmap.org/browse/way/71638376
and being part of the relation "Lake superior" as "inner" polygon:
http://www.openstreetmap.org/browse/relation/1120169

Second time with several polygons or simple ways:
http://www.openstreetmap.org/browse/way/71638569
http://www.openstreetmap.org/browse/way/71645461
http://www.openstreetmap.org/browse/way/72372507

being part of 3 relations of type "multipolygon" as "outer" and tagged with "natural=wood":
http://www.openstreetmap.org/browse/relation/1117973
http://www.openstreetmap.org/browse/relation/1117939
http://www.openstreetmap.org/browse/relation/1117953

As you can see, the same surface is identified twice as "natural=land" and "natural=wood". Then the renderer will probably select only one of them, depending how the order of the data is processed and the rendering styles which varies at the different zoom levels.

To fix this, a better modeling would be to delete the 3 artificial polygons, keep only the coastline ways, remove the tag "natural=land" in the Lake superior" relation (but keep its "inner" role), and merge the 3 "natural=wood" multipolygon relations into a single one (with the same tags).

permanent link

answered 28 Feb '13, 10:18

Pieren's gravatar image

Pieren
9.7k2075157
accept rate: 15%

edited 28 Feb '13, 10:19

1

Is any of the QS tools able to detect such problems?

(28 Feb '13, 11:58) mmehl
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question asked: 27 Feb '13, 22:06

question was seen: 1,959 times

last updated: 28 Feb '13, 11:58

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