[Routing] Driving directions web map

[Tristram Gräbener]

Hi

I agree that it would be nice to have some general format for routing.

Wouldn't it be nice to have a format somewhat close to the formats
available for commercial databases (like Navteq or Teleatlas) ?

I have (limited) experience with Navteq:
The arcs are traditionnal (source, target) but also have a "geometry"
property allowing to represent graphically the link (a string of many
points). The limitation is that the properties are "hard coded" and
makes extension more difficult.

I am working (but you know... never enough time :'( ) on a parser to
postgis (massively based on osm2pgrouting). From that database it will
be possible to export it to quite many different common formats (using
ogr2ogr). This would allow to use the data as a drop-in in many GIS
that weren't designed for osm data (osm2postgis works quite well, but
doesn't split the ways in elementary arcs, thus is quite useless for
routing). PGrouting only requires a table with source, target, cost,
[rcost] so, nothing very complicated.

I have the feeling that there are two approaches generaly used :
* splitting ways into elementary arsc
* merging nodes of degree 2
I don't know if one approach is better than another... If you have any
opinion on that question I'm interested.


Greetings from Toulouse

On Thu, Oct 9, 2008 at 4:26 PM, Frederik Ramm <frederik at remote.org> wrote:
> Hi,
>
> flo wrote:
>> Are there any approaches to 'normalizing' or 'layering'?  (like freeway-
>> / primary- / secondary Graphs)?
>
> Every routing software/project does their own preprocessing. Navit has
> its own compiler, gosmore has a built-in compiler for creating an
> indexed tree file, openrouteservice uses unreleased code to create their
> routing graph inside a database.
>
> At one time I thought about making general preprocessed routing graphs
> available on the Geofabrik web site in regular intervals but I then
> decided not to as every routing software has its own style anyway, doing
> different things in the preprocessing step.
>
> (If, however, members of this list come up with some generalized format
> for an OSM routing graph plus the algorithm that creates it, then I'd be
> happy to look into providing such a routing graph available to all on a
> regular basis. Does pgrouting have something like a recommended general
> graph structure that would be suitable an usable to many?)
>
> Bye
> Frederik
>
>
>
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