[OSM-dev] (Multi)Polygon handling

Jochen Topf jochen at remote.org
Fri Jul 13 18:45:49 BST 2012

On Fri, Jul 13, 2012 at 04:22:24PM +0200, Colin Smale wrote:
> 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.

Thats what I am saying. The winding order should not be significant.

Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298

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