On Thu, Jul 22, 2010 at 11:08 AM, Dylan Semler <[email protected]>wrote:
> > > On Thu, Jul 22, 2010 at 5:57 AM, andrzej zaborowski <[email protected]>wrote: > >> On 11 July 2010 10:23, Maarten Deen <[email protected]> wrote: >> > If you have a layout like this (use a fixed-width font): >> > >> > | | >> > A----+-+ >> > | +----B >> > C----+-+ >> > | | >> > >> > And you want to go from B to A, why would routing software say "go >> straight >> > on" and not "go right, then go left"? >> >> My opinion is that it is a routing software issue after all. When a >> road segment is just about 5m long, the software should just skip it >> in the driving directions and look at the angle between the A and the >> B roads. It can go as far as doing what Alan said, i.e. join all of >> the nodes in a junction (a concentration of nodes where roads meet) >> into a single node, possibly in the preprocessing phase. I don't >> agree that this should be done in OSM data, it will prevent more >> clever routing direction being given when more clever routing software >> is written (e.g. software telling your car where to stop to wait for >> green light, which lane to take etc). >> >> The lengths need to be chosen carefully because in e.g. pedestrian >> routing, 5m may be significant (say you're looking for an exit from a >> maze). A car can't even make turns that tight, and you're interested >> in the bigger picture when you reach a junction, the routing is not >> clever enough to get you through a junction anyway. >> >> > >> > And option is to map it like this: >> > | | >> > A----+ | >> > |\| >> > | +----B >> > |/| >> > C----+ | >> > | | >> >> > How about grouping all of the nodes of the intersection into a relation? > Routing software can treat it as a single intersection and the map can > reflect how the roads are actually laid. > Actually, I see there already is a proposed feature to use relations to handle routing instructions for complicated turns[1] [1]http://wiki.openstreetmap.org/wiki/Relations/Proposed/Turn_hints
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