[OSM-talk] Best way to draw areas with holes?

[Dirk-Lüder Kreie]

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Martijn van Oosterhout schrieb:
> On Dec 20, 2007 11:44 PM, Alex Mauer <hawke at hawkesnest.net> wrote:
>>> I have used the multipolygon relation to draw islands in rivers.  It is specifically intended for drawing holes in areas and worked very well for me.
>>>
>> I've tried to use it for this, but I run into problems when the river
>> bank is too large for a single way.  (I split the ways at 129 nodes, but
>>  the exact number doesn't matter)
> 
> "polygon with holes" and "splitting outside into peices because it's
> too long" are incompatable, you either do one or the other. A
> riverbank has to be a single closed polygon, the only area feature
> exempt from this rule is "natural=coastline".
> 
> TBH, I'd forget the multipolygon stuff and draw the islands as
> natural=land or some such...

I would not do so, for a number of reasons, especially when the area in
the "inner" part is really not a part of the outer polygon (is an island
part of the water area?) and it also creates a number of rendering
funniness:

http://geo.topf.org/comparison/index.html?mt0=mapnik&mt1=tah&lon=4.490018&lat=51.9153147&z=14

- --

Dirk-Lüder "Deelkar" Kreie
Bremen - 53.0952°N 8.8652°E

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