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.
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