[Tagging] Through_route next steps

[fly]

On 15.06.2013 17:00, Eckhart Wörner wrote:
> Hi Rob,
> 
> Am Samstag, 15. Juni 2013, 13:33:24 schrieb Rob Nickerson:
>> The next steps with any tag proposal that reaches a hung jury is to read
>> through the comments and update the proposal to address the issues raised.
>>
>> In this case I think the wiki page needs to be clearer about what this tag
>> is for (a few photo/aerial image examples would help), and how it differs
>> from other tags.
> 
> I don't think the rejection of the proposal is based on missing illustration.
> In my eyes, the proposal almost completely misses the underlying problem:
> the representation of data in OSM is unsuitable for inferring turn instructions.
> 
> The closest thing to a junction in OSM right now is a node: if there are three
> or more points connected to a node, we call it a junction.
> Let's talk a bit about that node: how should we infer routing instructions
> from the constellation of ways connected to that node? Should we take the
> classification of the road into account? Most OSM routing programs are
doing an
> exceptionally bad job at this, and yet they are not to blame; since
the only
> way they are actually able to work is by applying heuristics, and the
reason
> for that is simple: there are no conventions *at all*.
> 
> The second problem is that a junction is not necessarily node-like at all.
> Think about divided highways. Or think about links, and you'll soon realize
> that turns can have an extent as well.
> 
> A third aspect of the problem is that even if you are perfectly able to deduce
> appropriate turn instructions from the geometry, you may still end up
with turn
> instructions that differ from what the signs say. Deviating from the
signs is
> probably not a good idea unless your plan is to confuse the user.

+1

@Rob:
Did you ever try to describe the junction with the Lane and Road
Attributes [1] ?
This scheme should allow to indicate the proper lanes to take the turn
from and should solve your motorway example without turn lanes.

fly

----
[1] https://josm.openstreetmap.de/wiki/Styles/Lane_and_Road_Attributes