[OSM-dev] Polygons in OSM don't necessarily comply to simple feature specification

Christopher Schmidt crschmidt at metacarta.com
Wed Apr 16 23:31:49 BST 2008


On Thu, Apr 17, 2008 at 12:15:16AM +0200, Frederik Ramm wrote:
> Hi,
> 
> > The only exceptions apparently  
> > being that self-intersecting polygons are allowed in OSM. 
> 
> The wiki page you cited says "In general, a 2D geometry is simple if
> it contains no self-intersection." - what do they mean by "2D
> geometry"? Specifically, would a self-intersecting *line* be allowed?
> (I like to think of points as 0D, lines as 1D, and areas as 2D but I
> have a feeling the GIS people might view this differently?)

"Geometry in a 2 dimensional plane." In a 2 dimensional plane, all
geometries are 2d, because you specify their coordinates in two
dimensions. 

Regards,
-- 
Christopher Schmidt
MetaCarta




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