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 <[email protected]
<mailto:[email protected]>>:
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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