[OSRM-talk] OSRM match service for public transportation
Nate Wessel
nate.wessel at mail.utoronto.ca
Thu Apr 26 20:11:28 UTC 2018
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
> <mailto: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 <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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