Speed parameter

[fagnersutel]

What is the speed parameter in the osrmIsochrone.R file? In the walking parameter we have 10 * (1000/60)? Is it miles, kilometers/h?

[rCarto]

speed is expressed in meters per minute. For walking we use a theoretical value of 10 km/h, for driving 120 km/h.

This variable is used to get the theoretical maximum (euclidean) distance reached within the maximum breaks time value (and then compute a regular grid within this extent and return time distance in this grid, compute isopolygons etc.).

[fagnersutel]

Great, so if I want to make an isochron for kids around a school; is it possible to edit the osrmIsochrone.R file to adjust the walk to a factor that reduces this speed? Of course making a clone of the package.

[rCarto]

Nope, that would not be useful. This parameter only define the extent of the grid internally needed to get measures. If you want a custom speed (walking slowly, running...) to be used in time distance calculation by OSRM, you'll need to use your own instance of OSRM server and use a custom profile (editing a *.lua profile file from OSRM server GitHub repo for exemple) in it.
osrm, the package, does not compute the time/distances measures, the OSRM server does.

[edit]

• A link to a profile file in OSRM: https://github.com/Project-OSRM/osrm-backend/blob/master/profiles/foot.lua
• How to set up your own OSRM server instance with docker: https://github.com/Project-OSRM/osrm-backend#using-docker

[/edit]