graham wrote: > - Say I have a bus lane (or cycle lane) running along one side of a > two-way road (the most common situation where I am). Just attaching a > 'left' tag to it makes it dependent on nobody ever reversing the > arbitrary direction attached to the way.
No, it doesn't, because editors would make flipping the left/right part of the "reverse way" command, just as they now flip "oneway"s and so on. There are various consistency checks editors need to do when making changes - this is just another one. > - More serious, I think: it just feels quite arbitrary as a solution: I > would have to tag a lane as being 'left' in relation to the random > direction the arrows on the way happen to be pointing, rather than in > relation to anything in the real world. How else do you unambiguously intrinsically define the side of a way? Unless it's a closed way, where you have "inside" and "outside", the only way is to give it a direction (which it has) and say "right" or "left". You can define it extrinsically using things like "north" or "west" but that runs into problems with roads which curve, or even run in a circle. > 2. have an 'origin' tag to be used on the first node of a way > independent of direction; if the way direction flipped, the origin would > stay in place. 'Left' or 'right' would be in relation to the origin > node. Still completely arbitrary where the origin goes, and how do you > find it on a long way? If my proposal has disadvantages, then this has them all but adds some new ones too :-) > 3. Make more of a separation between internal representation of ways and > user views in josm/potlatch. All ways have a direction which is > independent of the 'arrowed' direction which can be displayed to users, > and is fixed - a totally arbitrary value used only as a fixed reference. Why? Why not just use the arrowed direction? After all, it's not exactly complicated to flip tags when you change the direction of the way. That's why the scheme is generic :left and :right - so it can be used on any tags. Gerv _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
