[Tagging] Roles of route members (was: Merging tagging scheme on wiki pages of Hiking, ...)

Sarah Hoffmann lonvia at denofr.de
Sun Aug 18 08:58:42 UTC 2019

On Sat, Aug 17, 2019 at 01:11:17AM -0700, Richard Fairhurst wrote:
> Peter Elderson wrote:
> > I would like to see this software in operation! Could you give me the 
> > links of some applications 
> I use my code in the backend of cycle.travel. It's not open source. I've
> seen code used by one other OSM-based site and there's a further one that's
> clearly using something similar. There are at least two really obvious
> strategies for dealing with relations like this.
> > The point is, as it is it's not good enough for data use besides 
> > rendering. you can't rely on route relations for anything but rendering
> Once again: pretty much every OSM-based bike router uses route relations to
> influence routing. (That might give you a clue to one of the strategies.)

But this is a task which is essentially the same rendering. You only need
to know what routes are on a certain way segment and use that information
to adjust the weights for the road. Even if you do something fancy like
ensuring that you remain of the same cycling route, it still comes down to
using the relation information as a property of the ways. Our route relations
are well suited for that.

The problems come in if you want to go the other way. When you start with the
relation, want to determine where the route goes along. That information is
simply not contained in the route relations as long as you don't impose a
couple of restrictions. Sure, you can apply a couple of heuristics and get
a reasonably good result for most of the routes. But it remains guess-work.

I have no issue if relations require reasonable processing to get to a result
but I would like to see enough information encoded in the route relation that
the processing invariably gets me to the result that the mapper intended.
I consider sorting and the use of roles essential for that.


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