Option to set speed in the osrmIsochrone function about osrm

[rCarto]

Hello,
Ok, I will investigate the question of the default walking speed to obtain a grid large enough to contain the full isochrones.

The units for speed are in kilometers per hour.

[rCarto]

I may have find the problem.
Do you use the OSRM demo server (the default one used with osrm R package) or your own?
The OSRM demo server only serve driving distances. The use of driving distances for time calculation and walk profile for isochrone computation would explain your output.

If you use your own server you have to set the correct profile (foot.lua instead of car.lua) in the first step of the OSRM server build...

see also #37

[annnvv]

I am using the demo server. I didn't realize that the demo server only allows for driving distances.

I appreciate you taking the time to look into this, thank you.

[MeganBeckett]

Hi there, I have also been investigating this and from what I can see where speed is calculated in the function (https://github.com/rCarto/osrm/blob/39906d3ce00592bc622a6e2091c4c878b1f1f743/R/osrmIsochrone.R#L79), are the units really in km/hr?

Or meters/minute? Even so, the speed for "walking" then equates to 166 m/min - is that correct? That's nearly 10km/hr which is faster than most people can run?

Also, is it possible to set your own speeds for walking and driving?

Thanks!

[rCarto]

Hi,
This speed is only used to create a grid to query travel times. So I used over-estimated speeds to have a grid large enough. The walking, driving and cycling speeds are defined at the OSRM server level through different profile files: https://github.com/Project-OSRM/osrm-backend/wiki/Profiles.
The original issue has been replied above, the problem came from the use of the demo server.