Speed assumptions for walking/hiking unclear

[najusten]

Hello,

I’m 3 weeks into the world of ORS and QGIS for a thesis and the tool has been incredibly helpful so far so first off thank you for all the functionality!

I have a question about the assumed walking/hiking speeds - I read in another forum post that this is taken to be 5km/h unless an sac-scale is specified for a certain section of trail in which case it’s 2km/h.

To provide some context I’m looking at isochrone walking catchments (30, 60, 120min) in rural Africa so a lot of the speed limits, etc. will be default values for certain road/trail classifications I assume.

• What exactly is a sac-scale in the context of walking? Here (GitHub - GIScience/openrouteservice-docs: This repository stores the swagger specifications of the openrouteservice API. Browse to swagger for a detailed overview.) when looking at sac-scales there is a reference to mountain biking etc. which confused me slightly? So if a trail is a mountain bike trail (for example) the assumed speed is reduced to 2km/h?
• How do I check if a route (or which routes) has an sac-scale associated with them?
• How is walking different from hiking when calculating time catchments?
• In the absence of sac-scales is gradient information neglected when calculating isochrone walking/hiking time catchments? How could this information be factored in? (such as Tobler’s hiking formula based on gradient information)

Thank you in advance for all your help!

[jschnell]

Hey,

for an explanation of the SAC-Scale, have a look at this osm wiki article.
It is in general a classification of a paths “difficulty” for hiking. For mountainbiking, there exists a separate mtb-scale.

You can check if a route has a sac-scale associated with it by requesting trail difficulty as an extra info in your request.
Have a look at our documentation on the meaning of the returned values.

Alternatively, you can view the way in question on the OSM directly, and it’ll show you whether there’s a sac-scale tag. Use the “pointer w/ questionmark”-button on the right on OSM for this.

Walking is different from hiking in that it allows SAC-Scales as high as T1 only, speeds do not differ.

Yes, currently gradient information is ignored when calculating routes or isochrones. Unfortunately, this is not an easy problem, have a look at this issue or search the forum on reasons why - it tends to generate weird routes for weird reasons.

If you use the openrouteservice programmatically, it should be rather easy to factor in the steepness to adjust the times of routes calculaed.

I hope this answers your questions,
best regards