[OSM-talk] enclosed areas => borders

Marcus Wolschon Marcus at Wolschon.biz
Sat Feb 7 06:34:19 GMT 2009

On Sat, Feb 7, 2009 at 4:17 AM, Franc Carter <franc.carter at gmail.com> wrote:
> Hi,
> I am working on how to import the Australian suburb boundaries. I have
> these as a set of shapefiles that define an enclosed area for each suburb.
> The suburbs share many points in common and the outline of one
> areas overlays the outline of the neighbouring suburb(s) as would
> be expected.
> It's fairly easy to de-dupe the points that make up the shape, but I'm
> struggling with the next part I want to do. I'd like to split the areas in
> to
> sets of borders between the two adjoining suburbs. While I believe I have
> an approach, it's looking annoying and complicated.
> So, does anyone know if there is a 'standard' algorithm for doing this ?

How many nodes do 2 typical suburbs share?
Many programs (like the adress search in my navigator) cannot yet use
borders split up into multiple polylines grouped in an ordered relation.
Considering that relations are not ordered until api 0.6 is public.
(This is what is done for country-borders.)

If it's not too many points on the shared polylines I see no problem with
sharing just the nodes and having closed polygons for the  suburbs
as more programs will be able to make use of them.


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