Anthony wrote: > 2009/11/26 Morten Kjeldgaard <m...@bioxray.dk>: >> So for example, if the multiplex in the example represents an intersection, >> you would connect B->D (left turn from B), B->F (going straigh ahead from >> B), B -> D (right turn from B). And so on, to make all other possible >> connections inside the intersection. This would give you an object which >> would render nicely as an intersection, and there's of course the option of >> tagging a bunch of auxilliary information such number of traffic_lights, >> directional signs etc. > > How would you measure the distance from, for example, B->D? It's not > a straight line. > > A minor error, I suppose, for an intersection, especially a simple > intersection like the one you've outlined, but if the concept is going > to be extended beyond intersections, the error could potentially be > expanded as well. And if we're going to take the time to carefully > micromap an intersection as an area, we might as well be as accurate > as possible.
Good question :-) It is indeed true that this concept could be expanded to deal with, say, a six-lane highway, a cloverleaf intersection, etc. Fascinating... Well, the internal connections would be constructed from nodes and ways inside the object (but encapsulated from the outside world, so they are only accessible from the object/multiplex itself.) Therefore, the object knows the length of it's internal connections and should be able to answer that question. (Perhaps it sounds like I'm talking about a C++ object but I hope you get the meaning.) In the meantime, I've elaborated a little bit on this idea, illustrated with somewhat more detailed pictures of the intersection. It's on my wiki page [0]. I made these before starting to think about your question, so the internal connections you see in one of the image are made up of just straight lines. It does, however, deal with the internal routing in the object. Like you said, it would give errors when attempting to measure distances, but in the case of an intersection those errors would be extremely small (the object would have to measure the distance from B to the node that branches off to D plus the distance from there to D, ignoring the fact that a car would take a shorter curve through the intersection.) Cheers, Morten [0] http://wiki.openstreetmap.org/wiki/User:Mok0#Multiplex_suggestion _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
