<html><head></head><body>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.<br>
An alternative is a full mesh network, where every possible entry node is directly connected to every possible exit node.<br>
--colin<br><br><div class="gmail_quote">On 28 July 2015 08:01:51 CEST, Maarten Deen <mdeen@xs4all.nl> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">On 2015-07-27 23:39, Lester Caine wrote:<br /><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"> On 27/07/15 20:55, Mike Thompson wrote:<br /><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; padding-left: 1ex;"> I assumed that when the wiki spoke about "routable" it was referring <br /> to<br /> the water flow rather than boat/ship/barge traffic. In any event, a<br /> routing engine for boats could use the presence of a dam or weir<br /> (combined with the absence of a lock) to deduce that ship navigation <br /> was<br /> not possible.<br /></blockquote> <br /> 'This way used should point in the direction of water flow' is only<br /> applicable to non-tidal flows, and reservoirs may well control water<br /> flow in a way that makes a 'water flow map' somewhat difficult to <br /> deduce.<br /></blockquote><br />Only if they are entirely
artificial. A dam in a river or stream makes <br />the direction of water very clear: high to low. Only when there is an <br />artificial reservoir with no natural tributary it is not clear.<br /><br /><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"> The use of 'routable network' is rather ambiguous, but this is little<br /> different to the problem of routing through other land based open areas<br /> where several waterway features link into an area of open water. The<br /> jury is still out on putting in all the paths through the area, but if<br /> there is a navigable route designated through a water body it should be<br /> drawn, but an imaginary link just showing water flow should not be<br /> necessary? Any routing process should be able to deduce the relation,<br /> there is no need to draw it.<br /></blockquote><br />Causality. Does a water area need a way indicating the direction of <br />water? Of is it
that when you draw a way through the water area it <br />should point in the direction of the water flow.<br /><br />Maarten<br /><br /><br /><br /><br /><hr /><br />talk mailing list<br />talk@openstreetmap.org<br /><a href="https://lists.openstreetmap.org/listinfo/talk">https://lists.openstreetmap.org/listinfo/talk</a><br /></pre></blockquote></div></body></html>