[OSRM-talk] OSRM match service for public transportation
Nate Wessel
nate.wessel at mail.utoronto.ca
Thu Apr 26 19:30:44 UTC 2018
You can use a profile to determine which edges are included in the
graph, which are accessible, etc. If for example you only handled subway
lines in the profile and disregarded all other data from OSM, you would
only be able to match things to subways.
A GPS trace from someone e.g. walking aboveground but parallel to a
subway track would also likely match to the subway rails because there
would be no more-likely candidates to match to.
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 02:32 PM, Patrick Agin wrote:
> 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
> <mailto: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
> <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
> <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 <http://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 <mailto: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
>> <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
>> <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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