[mkgmap-dev] Garmin bicycle routing algorithm

Tue Jul 21 15:39:12 BST 2015

Hello,

I apologize if this question is off-topic for this list. I am trying to 
get an idea about how the bicycle routing of Basecamp 4.4.8 works (or 
eTrex 20x, which is the unit I have) and how it differs from 
car/automotive routing. I wonder if others in this list could enlighten me.

 From the information I was able to gather, automotive routing works 
like this:
- fastest speed: gives preference to higher road_class
- shortest route: disregards road_class, calculates shortest route
In both cases road_speed is only used for ETA and not route calculation 
(or has a very low weight).

However, does bicycle routing works in the same way? I found confliction 
information on this point: when using 'fastest speed', some say that 
*lower* classes are preferred (due to roads being less busy) but most 
dedicated cycle maps that I have encountered (for example ligfietser's 
most excellent OpenFietsMap) use higher classes for more desirable roads 
and claim that the map can be used in both automotive and bicycle mode. 
And what about 'shortest route': does it disregard road_class like 
automotive mode?

And how 'bicycle' and 'tour cycling' differ?

I'm going to create a custom OSM map and a custom style in order to get 
some more clues and share the findings with the list but I would 
appreciate if somebody with the knowledge could shed some light into 
these issues.

Cheers!
// Leonardo.