[OSRM-talk] OSRM match service for public transportation

[Patrick Agin]

Thanks again Nate, I will take a look for sure. But just out of curiosity,
what your ttc profile is useful for then? And how do you (in general, big
picture only) define in a profile that it's subway only? And does it mean
that when map matching against this profile, only subway routes will be
returned?
Patrick

2018-04-26 12:35 GMT-04:00 Nate Wessel <nate.wessel at mail.utoronto.ca>:

> This one won't return a subway route because I haven't configured it for
> that. I don't have subway trains in the dataset I'm working with for
> Toronto. But it would be pretty easy to make a subway only profile, or to
> add subways into this one if you want to do all transit modes in one
> profile. Take a look at this page for documentation on how profiles work:
> https://github.com/Project-OSRM/osrm-backend/blob/master/docs/profiles.md
>
> If you want to understand how map matching in OSRM works generally, I
> think this paper is a good place to start: https://www.microsoft.com/en-
> us/research/wp-content/uploads/2016/12/map-matching-
> ACM-GIS-camera-ready.pdf
>
> When you change the profile, you're essentially configuring the
> street/rail/whatever network that your GPS trace will match against.
> Montreal definitely has subways in OSM; you can see them in the main map at
> openstreetmap.org.
>
> Best,
> Nate Wessel
> Jack of all trades, Master of Geography, PhD Candidate in Urban Planning
> SAUSy Lab <http://sausy.ca>, Sid Smith Hall, University of Toronto
>
> On 04/26/2018 10:52 AM, Patrick Agin wrote:
>
> Hi Nate and thank you very much for your help. I have a very basic
> question about your ttc profile (sorry if it's too silly). When you match a
> GPS dataset against this profile instance, will it return a subway route
> for example? If yes, why this subway route would be declared much plausible
> by osrm than the street route? Only because of the ttc profile? I realize
> that I don't understand very well the involved mechanisms behind osrm and
> profiles, if you can shed some light on this, I would greatly appreciate.
> Another question: I suppose that the subway data has to be included in the
> osm data of my city (Montreal) in order to get subway routes from match .
> How can I know if it's there or not in my osm data?
> Thank you again Nate,
> Patrick
>
> 2018-04-26 9:36 GMT-04:00 Nate Wessel <nate.wessel at mail.utoronto.ca>:
>
>> I've had some success with transit matching by simply modifying the car
>> profile to allow routing on streetcar tracks, allowing access for buses and
>> public service vehicles, etc. Here's a profile I'm using for transit now:
>>
>> https://github.com/SAUSy-Lab/retro-gtfs/blob/master/etc/ttc.lua#L347
>>
>> I had also tried to develop a more transit specific profile from the
>> ground up. My thought was that known transit routes (provided in the OSM
>> data) would be preferred by modifying their edge weights. This however ran
>> into an issue with the matching service which hasn't been resolved yet;
>> edge weights simply aren't used in match results.
>> https://github.com/Project-OSRM/osrm-backend/issues/4785
>>
>> If anyone has a suggestion for the question about multimodal paths, I
>> would be very keen to hear it, however I suspect this is still an open
>> topic of research with no definite best practices.
>>
>> Best,
>> Nate Wessel
>> Jack of all trades, Master of Geography, PhD Candidate in Urban Planning
>> SAUSy Lab <http://sausy.ca>, Sid Smith Hall, University of Toronto
>>
>> On 04/26/2018 09:01 AM, Patrick Agin wrote:
>>
>> Dear all,
>>
>> I'm a newbie to routing engines and my first attempts are with OSRM.
>> Specifically I want to use the *match *service. Questions I have is :
>>
>> 1) is it possible with match service to specify public transport (e.g.
>> subway) as the mode of transportation? I see only profiles for car, bike
>> and foot. If not, is there a solution? I'm pretty sure it it possible but
>> how? I saw in some profiles the public_transport parameter but I don't know
>> how to use it.
>>
>> 2) is it possible for match to return a multi-modal path given the
>> timestamps of each coordinate? For example, return a sub-path that is the
>> most plausible for pedestrian (chosen because of the low speed inferred
>> from timestamps) followed by another subpath that is the most plausible for
>> car (because of a higher speed)? Or is the only solution to pre-process the
>> data to infer by myself the mode of transportation and make subsequent
>> calls to the corresponding profile instance?
>>
>> Thanks a lot,
>>
>> Patrick
>>
>>
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