[Routing] How to handle lack of connectivity within the routing graph?

[Mark Williams]

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David MENTRE wrote:
> Hello,
> 
> While playing with routing is OSM map, I have observed that the OSM map
> is not fully connected if you consider only the routable ways[1]. For
> example, the map or Rennes city, France[2] appears to be made of 3335
> ways divided into 8 different connected components.
> 
> With such a divided map, sometimes there is no route between two points
> if those points are in two separated components.
> 
> Has anybody any idea how one should handle this?
> 
>  * Should I consider having a bug in my program? (not entirely excluded
>    ;-) For example, a bad interpretation of way attributes;
> 
>  * Is this a "bug" in the OSM data (error made by people or lack of
>    enough data)?
> 
>  * In the above case, are other routing programs (e.g. recently
>    announced Gosmore) using some kind of "tricks" to join the separated
>    components (e.g. consider two way points so close that they are the
>    same point)?
> 
> Sincerely yours,
> david
> 
> Footnotes: 
> [1]  Ways with the "highway" attribute with following values:
>        | Motorway
>        | Motorway_link
>        | Trunk
>        | Trunk_link
>        | Primary
>        | Primary_link
>        | Secondary
>        | Tertiary
>        | Unclassified
>        | Track
>        | Residential
>        | Living_street
>        | Service
> 
> [2]  http://www.openstreetmap.org/?lat=48.1157&lon=-1.6625&zoom=13&layers=B0FTT
> 

Hi,

I had a quick look at the city in JOSM & found only one typical Potlatch
 node-not-connected-to-way junction; many (440) overlapping ways though,
most of which are areas - I haven't been over these to see if any are
streets not connected right.

Took out most of the crossing-way errors, but they're mostly waterway &
tunnels.

It all looks pretty connected to me! Also a quick Pyroute across the
town worked fine.

Are you using capitalised values for highway as written above?


Mark
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