On Sun, Oct 12, 2008 at 9:13 AM, Gervase Markham <[EMAIL PROTECTED]>wrote:
> 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 > Just as a note, someone already added automatic left/right tag changing to JOSM when a way is reversed. It works for a few different schemes, including :left and :right. Karl
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