[OSM-dev] Polygons and Multipolygons

Artem Pavlenko artem.mapnik at googlemail.com
Fri Feb 8 12:16:03 GMT 2008

On 8 Feb 2008, at 11:58, Richard Fairhurst wrote:

> Frederik Ramm wrote:
>> True. What we had been looking for was a term for "polygons with
>> holes"; it seemed unreasonable to create a relation "type=polygon" as
>> plain polygons, without holes, don't require relations. But
>> multipolygon is somewhat of a misnomer.
> It would be a "compound path" in Illustrator.

Yes, indeed. Rendering software (including Mapnik) doesn't really  
care about geometrical correctness, because rasterizing algorithms  
work just fine with self-intersections etc. The problems are start  
popping in when you want to do some kind of analysis, i.e. calculate  
a buffer zone for the river basin.

I'm for keeping OSM model as simple as possible, but not simplistic.

> cheers
> Richard

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