If we can separate the flow direction discussion from the routing, the latter becomes a more generic "routing through areas" problem which has been discussed before in the context of pedestrian routing. The idea being that it should be possible to construct a routing engine to take you from any point on an edge of a polygon to any other such point, while remaining within the polygon boundary. An alternative is a full mesh network, where every possible entry node is directly connected to every possible exit node. --colin
On 28 July 2015 08:01:51 CEST, Maarten Deen <md...@xs4all.nl> wrote: >On 2015-07-27 23:39, Lester Caine wrote: >> On 27/07/15 20:55, Mike Thompson wrote: >>> I assumed that when the wiki spoke about "routable" it was referring > >>> to >>> the water flow rather than boat/ship/barge traffic. In any event, >a >>> routing engine for boats could use the presence of a dam or weir >>> (combined with the absence of a lock) to deduce that ship navigation > >>> was >>> not possible. >> >> 'This way used should point in the direction of water flow' is only >> applicable to non-tidal flows, and reservoirs may well control water >> flow in a way that makes a 'water flow map' somewhat difficult to >> deduce. > >Only if they are entirely artificial. A dam in a river or stream makes >the direction of water very clear: high to low. Only when there is an >artificial reservoir with no natural tributary it is not clear. > >> The use of 'routable network' is rather ambiguous, but this is little >> different to the problem of routing through other land based open >areas >> where several waterway features link into an area of open water. The >> jury is still out on putting in all the paths through the area, but >if >> there is a navigable route designated through a water body it should >be >> drawn, but an imaginary link just showing water flow should not be >> necessary? Any routing process should be able to deduce the relation, >> there is no need to draw it. > >Causality. Does a water area need a way indicating the direction of >water? Of is it that when you draw a way through the water area it >should point in the direction of the water flow. > >Maarten > > > > >_______________________________________________ >talk mailing list >talk@openstreetmap.org >https://lists.openstreetmap.org/listinfo/talk
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