[OSM-talk] Segments, ways and order

Matthias Julius lists at julius-net.net
Mon Jul 16 19:36:09 BST 2007


Nicola Ranaldo <ranaldo at unina.it> writes:

> Segment order is important for many cases, one_way rendering, areas and so on.
> But it may be that a segment from node x to node y, for a one_way street, 
> should appear as from y to x for one or more areas. Sometimes it's impossible 
> to "reuse" the same segments. One solution could be in general create new 
> segments with the same nodes id, but if this is admitted it may generate a 
> lot of duplicates segments and seems to me a waste of resources in a 
> topological model. Another solution could be in reuse an existent segment if 
> it has the right order or to create the inverse if it does not match. A third 
> solution could be in having software renderers compute the node order for 
> areas at runtime with smart algorithms. In this case it will exists only one 
> segment from x to y and will be reused for every way containing node x and y 
> without care for the order. This maximizes the topological model but may 
> create problems in areas with holes.

Another solution would be to do away with segments and have ways
reference nodes directly.

(I know this has been discussed before and a transition would not be
trivial.) 

Matthias





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