On Sun, Nov 1, 2009 at 8:32 AM, Martin Koppenhoefer <[email protected]> wrote: > 2009/10/31 Randy <[email protected]> >> Secondly, if adopted strictly, if forces the creation of a >> separate tag with identical functionality for the above ground case. > > Which does make sense. A tunnel going underground can be crossed mostly > without even noticing the tunnel while a street that is covered or inside a > tube at groundlevel will mostly be an uncrossable obstacle, so that the > impact of this difference is huge! The functionality might in some cases be > identical for who uses the tunnel / street, but it is not for the rest.
That's handled by the layer=* tag through, isn't it? I feel strongly that an underground tunnel should (at least potentially) be mapped differently than an alley with a roof. But the layer tag (and/or the bridge tag in the case of a covered bridge) is probably enough to make that distinction. If not there's always underground=no. I'm not 100% against calling an above-ground passageway a "tunnel", but I'd need to see more cases and I'd need a good alternate definition. In the longer term, there's going to need to be a way to map polyhedra which are more complicated than just a polygon plus a height. That's the only way you can really map these complicated buildings located on non-flat surfaces. I suppose this could be done today using relations, but it'd be better if first there were a three dimensional node, and prior to that it'd be nice to get a good public domain database of ground level altitudes above/below the WGS84 elliipsoid. I have no idea if something like that exists or not, but I'd say it's somewhat key - consumer GPSes just aren't accurate enough for altitude readings, while height above ground level is fairly easy to measure (there are apps for triangulation on some smart-phones). _______________________________________________ Tagging mailing list [email protected] http://lists.openstreetmap.org/listinfo/tagging
