[OSM-talk] The segments vs ways vs superways question again...

[Jochen Topf]

On Wed, Jan 03, 2007 at 01:04:00PM +0100, bvh wrote:
> On Wed, Jan 03, 2007 at 10:55:05AM +0000, Robert (Jamie) Munro wrote:
> > I wasn't thinking groups of groups, just segments belonging to more than
> > one group (i.e. the fact that it is part of a group with a name="My
> > little street" tag doesn't mean it can't also be in a group with
> > ref="A1" if it is part of a bigger road.
> 
> Thanks for clearing that up, but now I fail to see the difference
> between working with groups as opposed to working with tags?

There is a motorway with "ref=A1" in Germany, too. If you use groups,
you'll have two groups with highway=motorway and ref=A1, one in the UK,
one in Germany. If you only use tags, you can't distinguish them.

Note that you can't use "connectedness" here as an added criteria. For
one some motorways have "holes" in them. And even if that wasn't the
case you'll get into trouble if you only look at an area in a certain
bounding box. One motorway might cross into and out of that area several
times and you can't see any more that it is the same motorway.

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