[OSRM-talk] Map-matching transit vehicles: giving preference to known routes?

[Nate Wessel]

Hi all,

I have recently been using OSRM to do map-matching for transit vehicles, 
with locations from historical GPS data. The documentation on creating 
profiles is pretty minimal from what I can tell, so I've just been able 
to make a few modifications to the car.lua profile to allow vehicles to 
go on streetcar tracks, agency service roads, etc.

The data I've been playing with so far has a ~20second sampling 
frequency, which has worked well, but I'm about to start working with 
data that has a lower sampling rate (30-60secs) and I'm worried that 
I'll get a lot of spurious matches. I was wondering if it is possible to 
modify the profile such that a strong preference is given to known 
transit routes (which are tagged with route relations in OSM). Transit 
almost always follows a known route, but sometimes it detours, and it's 
important to my research to be able to capture that in matched GPS data.

What might be a good way to add this to a routing profile? Does 
everything in the profile come down to speed, access, and node-related 
penalties? Would I want to artificially inflate the "speed" of 
transit-served streets? Is there more thorough documentation on profiles 
somewhere than what is provided here 
<https://github.com/Project-OSRM/osrm-backend/wiki/Profiles>?

The profile I've been using is:
https://github.com/SAUSy-Lab/retro-gtfs/blob/master/etc/ttc.lua

Any help would be greatly appreciated!

-- 
Nate Wessel
Jack of all trades, Master of Geography
SAUSy Lab <http://sausy.ca>, Sid Smith Hall
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