[OSRM-talk] Zlevels and Restrictions

Stephen Woodbridge woodbri at swoodbridge.com
Thu Nov 28 04:04:10 UTC 2013


I'm read over the documentation again and I am confused by the "Graph 
representation" wiki page.

I have a correctly noded graph in pgRouting. By this I mean that all 
intersections have a node(s) at them and there are no unnoded intersections.

One of the characteristics of this is the fact that segments at an 
overpass/underpass intersection are not really connected because with 
zlevel information we have assigned separate nodes for the over pass 
node from the underpass node, in spite of the fact that they both have 
the same 2D x-y locations (ie: they are separated in Z).

The "Graph representation" page seems to imply that all segments with 
shape points are exploded into multiple straight line edges with the 
idea that crossing polylines with a common x-y point will become noded. 
Is this true? Or am I reading too much into the description? It might be 
that this is a reference to how the OSM extraction process behaves, 
which seems to validated in the "Processing Flow" page.

More importantly, If I feed OSRM a graph via the normalized file format, 
what if any changes are made to my data inside OSRM?

Do I need to create No U-turn restrictions to all my two-way street 
segments or are these still created automatically at all nodes on 
two-way segments?

If I'm generating a normalized formatted file, then I do not have LUA 
scripts for the extraction process, but it seems that osrm-routed needs 
them to run. I would like to know how to generate these with different 
profiles if that is possible so that they match up with the data I put 
into the normalized file.

I'm happy to write up or add to existing pages as appropriate if you 
provide some guidance to these questions. Sorry I know that this is a 
lot to ask but I want to start tackling the turn restrictions and 
converting some real data to ORSM rather than the silly grid I was 
playing with before.

Dennis, the share memory write up was excellent. Thanks for that!


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