[OSM-talk] enclosed areas => borders

Franc Carter franc.carter at gmail.com
Sun Feb 8 01:03:43 GMT 2009

There are over a million points defining all the suburbs that are in the
data set.
90% of these nodes are going to be shared at least two suburbs as the only
where suburbs don't border suburbs is at the coast.

It's not clear as to whether which format the data should be imported yet,
the talk-au
list is discussing this at the moment, personally I am not leaning either
way at the moment.

However, I still want to be able to split the areas up, even if I put them
back together again.
I want the option of doing curve simplification, and this gives bad results
if it's done on
two closed areas that share nodes.

On Sat, Feb 7, 2009 at 5:34 PM, Marcus Wolschon <Marcus at wolschon.biz> wrote:

> 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.
> Marcus

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