[Tagging] Highway property proposal "covered=yes"

Anthony osm at inbox.org
Sun Nov 1 15:54:01 GMT 2009


On Sun, Nov 1, 2009 at 8:32 AM, Martin Koppenhoefer
<dieterdreist at gmail.com> wrote:
> 2009/10/31 Randy <rwtnospam-newsgp at yahoo.com>
>> 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).




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