[Tagging] Chaos and uncertainty in "bridge"

[Ben Johnson]

Hi Martin,

Your proposal makes a lot of sense. 

bridge:structure (or type) seems the logical place to put it, along with bridge:name, bridge:clearance (or whatever min/max clearance tags we have for tidal situations), etc...

The principal should also be extended to tunnels. 

eg tunnel:structure, using values like - "excavated" (shallow cut and cover tunnels), "bored" (deeper tunnels), and "covered" (ground-level tunnels enclosed by a building/structure).

BJ


On 17/01/2012, at 3:32, Martin Koppenhoefer <dieterdreist at gmail.com> wrote:

> Currently the documented values for "bridge" don't seem to follow any
> (single) classification system.
> http://wiki.openstreetmap.org/wiki/Key:bridge
> 
> Fortunately 98.49% of all actually used values don't have this problem
> (they are "yes"), but the rest seems a mess:
> 
> 1. There is a first classification system using the kind of way going
> over it for distinction:
> 
> 1.1 A road (or railway): "viaduct" (a term that is not really well
> defined, especially the distinction between a "bridge" and a "viaduct"
> doesn't seem to be clear). This is a bit mixed because besides the
> road this seems to be a bridge with several abutments in "small"
> distances, whatever "small" is, and "viaduct" seems to be used also in
> conjunction with railroads. Not sure but I feel as "viaduct" might
> also be a bridge typology (see 3).
> 
> 1.2 Water: "aqueduct" (suitable for the parts of aqueducts that span
> over a void). The definition seems to extend the use to all kind of
> aqueducts ("A longer structure for carrying a canal or fresh water.")
> while many aqueducts are not spanning over something (they are tubes,
> have a solid support like a wall without openings or even are
> underground) so they clearly aren't bridges.
> 
> This first system doesn't make much sense IMHO, because you can
> already see by other tags which kind of way is on top (waterway,
> highway, railway), but it is currently the most used.
> 
> 
> 2. Another classification system on the page is one according to the
> structural system employed:
> 2.1 arch
> 2.2 pontoon
> 2.3 suspension
> 
> 3. And even another system is that of typology:
> 3.1 bascule
> 3.2 drawbridge
> 3.3 humpback
> 3.4 lift
> 3.5 swing
> 
> 
> "so why is this bad?" one might argue. Well, the problem is that with
> this chaos you won't be able to tag all properties (typology,
> structural system, carried way) of a bridge, you will instead have to
> decide which one to focus on (might also lead to tagging wars).
> Another problem is that the lack of systematics makes it difficult to
> extent this system with new values, because it is not clear where the
> focus is.
> 
> 
> I propose to use distinct tags for these properties instead:
> 
> 1. is not needed IMHO (see above). If the interesting fact for
> viaducts are the several "small" spans I'd put this into typology.
> 2. could be tagged with bridge:structure (or structure or structural_system)
> 3. could be tagged with bridge:type (or type).
> 
> 
> 
> Last but not least I'd like to ask you for comments on 3 new values:
> N1. a bridge made of few ropes where you walk on a rope:
> http://bauwiki.tugraz.at/pub/Baulexikon/HaengeSeilBrueckeB/Kaiserschild_1.jpg
> http://www.gruppenstunden-freizeit-programme.de/ferienlager-freizeiten-erlebnisse/freizeit-bilder/seilbruecke/Piratenlager-05-262.JPG
> http://www.bergsteigen.at/pic/d6025434-21f9-4d93-9ce9-42aba5cf00db.jpg
> 
> additionally we could tag the amount of ropes (or even more precisely
> the amount of "upper" and "lower" ropes)
> 
> are these described in English with the term "zip-line"?
> http://en.wikipedia.org/wiki/Zip-line
> 
> 
> N2. a similar bridge made of ropes, but you walk on planks:
> http://bauwiki.tugraz.at/pub/Baulexikon/HaengeSeilBrueckeB/Trift_Bruecke_1.jpg
> http://bauwiki.tugraz.at/pub/Baulexikon/HaengeSeilBrueckeB/Tripsdrill.jpg
> 
> I guess this would be a "simple_suspension_bridge"
> 
> 
> N3. A "Cable-stayed_bridge" (the absence of this value makes it
> probable that most of these might currently be tagged as suspension
> bridges or not classified at all). The difference from a suspension
> bridge is that the cables are directly attached to the towers / pylons
> instead of to another cable, see here:
> http://en.wikipedia.org/wiki/Cable_stayed_bridge
> 
> cheers,
> Martin
> 
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