[OSRM-talk] OSRM match service for public transportation

Thu Apr 26 20:26:01 UTC 2018

I promise I'll try! But could you maybe just give me an example of how to
specify the inclusion of a subway edge?

2018-04-26 16:11 GMT-04:00 Nate Wessel <nate.wessel at mail.utoronto.ca>:

> Precisely. I would suggest using the profile documentation to build a
> simple profile from the ground up. The default profiles are very
> complicated and take advantage of some features of the Lua language that
> you may not understand when you first look at them. I didn't. I do believe
> the profile documentation is pretty complete though; the default profiles
> just have a lot of complex stuff built on top of that.
> 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 04:00 PM, Patrick Agin wrote:
>
> And by "handle subway lines", you mean "specify that only subway edges are
> included"?
> Can I ask you to point in .lua profile where you specify such a thing? In
> restricted_highway_whitelist structure maybe?
> The readme on profiles seems good but it's general (for example, there is
> nothing about this restricted_highway_whitelist).
> Do you know where can I find a complete tutorial/documentation on writing
> profiles?
> thanks again Nate
> Patrick
>
> 2018-04-26 15:30 GMT-04:00 Nate Wessel <nate.wessel at mail.utoronto.ca>:
>
>> 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>:
>>
>>> 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/doc
>>> s/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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