[OSM-dev] (Multi)Polygon handling

Colin Smale colin.smale at xs4all.nl
Fri Jul 13 15:22:24 BST 2012

On 13/07/2012 16:05, Jochen Topf wrote:
> On Fri, Jul 13, 2012 at 03:24:47PM +0200, Even Rouault wrote:
>>> That sounds reasonable. But we need to agree on what is valid and what is
>>> treated as invalid. In the testsuite of closed ways that I commited to
>>> github I defined an output for every case, but I'm not sure if the inputs
>>> are valid. My guess would be:
>>> 1) Definitely valid
>> OK
>>> 2) valid
>> Why do you need to reverse the winding order ? I thought that the WKT convention
> Winding order should not be changed IMHO. It might mean something in specific
> cases, who knowns? It could be an optional feature.
> Jochen
Is there not a problem with making winding order significant, as a 
particular way can be shared between adjacent polygons? For example the 
common boundary between two admin areas. For the polygon on the left, 
the points within the way must be ordered north-to-south (for clockwise 
winding) whereas the polygon on the right will require south-to-north.


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