[Talk-transit] GTFS and the like

Patrick Brosi | geOps patrick.brosi at geops.de
Tue Apr 8 09:29:45 UTC 2014


Sean,

thank you for your answer. You are absolutely right, the problem of 
extracting vehicle routes from OSM data can get very complex and has 
various pitfalls. We have experimented with simple map matching 
approaches where station positions were understood as very sparse sample 
points, but personally I think this approach is not the best and yields 
suboptimal results.

However, we achieved very got results by using iterative shortest-path 
(Dijkstra) calculations for each trip and between each station on a 
network graph (for example OSM). This respects the fact that each trip 
of a route can have its own shape. The shortest-path algorithm can be 
implemented with special cost functions for each vehicle type (for 
example, trains making a u turn out of a station should be punished).
Our application is still in a very early state of development, but 
already produces usable results.

With this approach, it could be possible to quickly import bus routes 
into OSM that aren't yet represented there at all. These routes would 
have to be checked and corrected by hand, of course, but we
expect the station-to-station-shortest-path shapes of bus lines to be 
nearly equal to the "real" shapes.

This is, of course, a top-down approach, and tools like TransitWand tend 
to be more exact because someone actually rode on the vehicle. However, 
for rural areas with low-density road networks and very few transit data 
enthusiasts, such an approach could be used to fill gaps in the data.

Patrick

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On 08/04/14 00:22, Barbeau, Sean wrote:
> Patrick,
>
> Thanks for the feedback!  If I recall correctly, we do have a basic
> route info sync, but it’s meant for route properties, not the spatial
> representation of the route.  You can view the route diff view here:
>
> https://code.google.com/p/gtfs-osm-sync/wiki/GettingStarted#Report_Route_Viewer
>
> However, I believe MapQuest’s XAPI changed shortly after we implemented
> this and removed the ability to get route information, and the feature
> currently isn’t functional.
>
> Routes can actually have several shapes based on the trip_ids and
> stop_times that run on different schedules or stop sequences.  So, this
> can get very complex and depends on temporal information as well.  In my
> opinion this would be a significant undertaking, and as I mentioned
> earlier I’m not convinced that maintaining temporal information in OSM
> is the best way to represent/store the data.
>
> No future plans to include such functionality as of now (our work is
> grant funded, and we currently don’t have funding source to continue
> development), although we’d be glad to accept contributions if someone
> else wants to take this on.
>
> On a related note, I think tools like Transit Wand have a lot of promise
> in assisting agencies/others in creating more accurate shapes.txt
> information:
>
> http://transitdata.openplans.org/
>
> Sean
>
> ----------------------------------------------------------------------
>
> Message: 1
>
> Date: Fri, 04 Apr 2014 14:36:25 +0200
>
> From: Patrick Brosi | geOps <patrick.brosi at geops.de
> <mailto:patrick.brosi at geops.de>>
>
> To: talk-transit at openstreetmap.org <mailto:talk-transit at openstreetmap.org>
>
> Subject: Re: [Talk-transit] GTFS and the like
>
> Message-ID: <533EA749.5080502 at geops.de <mailto:533EA749.5080502 at geops.de>>
>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> Sean, it would be interesting to know whether GO-Sync's processing
> includes the GTFS route shapes (the exact vehicle paths stored in
>
> shapes.txt) in any way. For example: if the GTFS feed only covers the
> location / attributes of stations and is missing shapes.txt information,
> does GO-Sync try to extract these shapes from OSM data? If so, what
> approach do you use? How are existing shapes compared to data already
> existent in OSM?
>
> Many public transport companies have very good data regarding the
> position of their stops, but lack the exact paths vehicles take between
> succeeding stations. In my opinion, providing not only the possibility
> to extract these shapes from existing OSM data but also the tools to
> edit them via OSM would dramatically increase the geospatial quality of
> many GTFS feeds.
>
> I just browsed GO-Sync's paper and couldn't find anything relating to
> this problem. Are there any future plans to include the functionality
> described above?
>
> Thank you!
>
> Best regards
>
> Patrick Brosi
>
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