Richard Bullock wrote: >Sent: 04 November 2009 9:39 AM >To: [email protected] >Subject: Re: [Tagging] Are tunnels only below ground? (Was > >> I concede. >> >> In fact my OLD Encyclopadia Britannica states that a tunnel is excavated >> underground and a "cut and cover" is not truly a tunnel. >> >> So the question now is how to tag an above ground "tunnel-like" structure >> to properly indicate it's characteristics, that is "completely enclosed >on >> all sides, save for the openings at each end". >> >We don't *have* to stick to dictionary definitions here when tagging, as >long as the meaning is clear; > >If it walks like a duck, talks like a duck, then define it to be a duck. > >I wouldn't hesitate to tag a cut-and-cover structure as a tunnel in OSM.
Agreed, the cut and cover approach is just the method of construction. The end result is still a tunnel in most instances as opposed to a long bridge. One way of telling the two apart is that typically the horizontal deck of a bridge sits on top of but is not integral with its side supports (abutments). In a cut and cover tunnel the deck/lid is normally integral with the sides to form a composite structure. > >A passageway through a building (but, say, without being inside that >building) is, to all intents and purposes, a tunnel. It doesn't necessarily >matter whether the "tunnel" is through a brick-built structure instead of, >say, a man-made earth embankment or natural hill. The question here is whether the structure is a building with a hole in it or a tunnel with a building attached. The tagging should logically fall out when you think about the overall structure first. > >By all means expand the tunnel key like others have done with bridge=* to >describe the tunnel properties; > >e.g tunnel = cut_and_cover / tunnel = avalanche_tunnel etc. > Agreed, though as a tunnelling engineer I'd probably call an avalanche tunnel a bridge in some cases on inspection, but I'd also expect the layman to tag it as a tunnel in most instances. >But I think the key here is that tunnel=yes should be allowable to get the >basic meaning across without an editor requiring to be an expert in tunnel >construction. Also agreed. The meaning is obvious if it has that tagging > >Of course there will be edge cases, but we don't have to go and invent a >million new keys to describe similar, but not identical, classes of object. > Cheers Andy _______________________________________________ Tagging mailing list [email protected] http://lists.openstreetmap.org/listinfo/tagging
