[OSM-dev] Keepright layer conflicts

[Ben Supnik]

Hi Y'all,

This is a very similar issue to what I found previously (with the thread 
"Creating 3-d connected network from ways + layer tag")...is it legal to 
link non-same-plane ways when a node's valence (number of line segments 
linking to the node) is more than 2.

In order to get sane results with existing data (which violate the 
keepright rules) I used the heuristic that line segments that dead-ended 
(when treated in isolation by level) had to be linked to something else. 
  This fixes the case where one road of an intersection is immediately 
on another layer because the bridge starts "at" the intersection.

It seems to me that for any areas not covered by keepright, this kind of 
error will keep appearing since there's a real-world situation (bridge 
starts at intersection) and the results look tolerable on the major map 
renderers.

cheers
Ben

Philip Homburg wrote:
>> I would prefer the wiki pages to be changed. It is clear that if the
>> bridge/tunnel does not end at the junction, that you need a short way between
>> them. But why should you need one if it _does_ end at the junction?
> 
> I very much prefer to keep the current consistency check (for roads at least,
> areas are another story).
> 
> In most cases, a layer change is also the start of a bridge (or tunnel) and
> bridges and tunnels just don't start at the middle of an intersection.
> 
> So there are just a few case where changing the rule may actually save some
> work.
> 
> Sometimes ways at different layers get connected by accident. Just disallowing
> layer changes at all intersections is much easier, robust, etc. then trying
> to specify which cases could be safe.
> 
> A couple of days ago, I correct a couple of situation where t-junction were
> created at different levels that were simply wrong. I think the chance that
> somebody will also create the extra ways as required by the current rule is
> quite small.
> 
> 
> 
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> 

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