80n escribió:
David
Was there a specific purpose you had in mind that needs to distinguish
between the main span of a bridge and it's ramps, or were you just
exploring the level of consistency in current tagging practices?
I wonder if we are approaching this problem from the right direction.
There are currently about 250,000 ways that are tagged bridge=yes.
Since there's no generally agreed definition of the extent of a bridge
every user will have used a different assumption and their own judgement.
Perhaps we should keep the vague and approximate definition that the
bridge tag provides, and instead propose extra tags that more
precisely define the lesser characteristics of a bridge. The bridge
tag as it currently exists, for all its vagueness, is easy to use and
effective.
For more precision we could consider additional tags that precisely
define the individual parts of a bridge. The addition of a
bridge_ramp tag, for example, could be used to indicate whether or not
a bridge includes or excludes the ramps.
bridge=yes, bridge_ramp=included|excluded
For those that want to define the extent of the ramps specifically
then a separate way would be required for each ramp and for the main
span, perhaps like this:
bridge=yes, bridge_ramp=yes
bridge=yes, main_span=yes
bridge=yes, bridge_ramp=yes
However, I'm not sure such an elaborate scheme would catch on much
unless there's a real benefit in tagging bridges to a greater level
of detail. That's why I wondered whether you have a specific reason
for wanting to tag bridges with more precision.
80n
On Thu, Jan 22, 2009 at 8:21 PM, Matthias Julius <[email protected]
<mailto:[email protected]>> wrote:
Chris Hill <[email protected]
<mailto:[email protected]>> writes:
> A bridge is usually there to cross something. So I would say,
> generally, what ever was built or built-up or added to make the
bridge
> function is part of the bridge. So ramps or approaches on
embankments
> even might well be judged to be part of the bridge. Maybe a note
> attached to briefly describe your decision will help future
OSMers. As
> always there are exceptions.
I'd day when there is air under the road it is part of the bridge, if
there is only a pile of dirt it is not part of the bridge. Even if
the dirt has been specifically piled up there to be able to get on top
of the bridge.
Matthias
im with Mattias here.
if there is air under the way i tag it as bridge, leaving the ramps out.
the layer of the way gives you the hint of the existance or not of ramps.
if the way is "layer=0" and the bridge is "layer=1" there is a ramp.
if the way is "layer=0" and the bridge is "layer=0" too
(the crossing way under is "layer=-1", digged)
then the bridge has no ramps.
so if we want to give more detail as to describe the ramp,
i would just tag the ramp as "bridge_ramp=yes"
and the airborn part of the way leave it as "bridge=yes"
i dont think there is need, as 80n said,
to tag all parts as "bridge=yes"
and then differentiate "main_span" and "bridge_ramp"
my two cents please
cheers,
sergio sevillano
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