On 10/08/2008 22:50, Gervase Markham wrote: > David Earl wrote: >> If you want to apply a bridge number to the bridge, there's no reason >> you shouldn't, vote or no vote. And if something were to render it, not >> doubt it would look right. >> >> However, the thing you are putting the number on has no easy linkage to >> the canal. If you were boating along the canal and wanted your satnav to >> pop up the next bridge number, it would have a hard time doing that >> because there's nothing actually linked to the canal to tell it. > > Ways intersecting the canal way, with a foo_ref attribute?
But they don't - bridges normally go over the canal in their own layer with no common node, just an crossing of ways which can, in principle, be computed from the geometry, but which is hard, and relies on the spatial positioning. If what you mean is using a way to link together the canal and the bridge, rather than representing a real feature, then that's using ways to do what relations are intended for, to link ways together in abstract ways. But as I said, if you tag the bridge (the road) with a canal bridge number, that'll do the job, just make it a lot harder to use in certain applications. What we're trying to say with a relation "this way goes over this way using a structure which itself has properties." Indeed the bridge is, again in principle but can be assumed in most cases, separate from the road (or whatever) it carries. (A case in particular point is a bridge carrying a dual carriageway where there is one bridge and two ways. Nearly all our representations of this are two (assumed) bridges at present, most of which are wrong assumptions.) David _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
