Thursday, June 17, 2010

Garmin GPS Routing Algorithm: How Does it Make Decisions on Routes to Take?

I've been trying to search Google for clues on garmin routing algorithm that it uses to make decisions on routes from one point to another.

I used to be an inter-network routing engineer, mostly using BGP and OSPF, to find the optimum path packets should take to reach the destination. GPS routing is no different, I know there are certain parameters to tweak in order to affect the route calculations Garmin GPS (like my Garmin Nuvi 1300) make.

This is not exhaustive but I know these parameters and certain tags matter but I still don't know which ones take precedence over the other in routing decisions:

1. Total distance (probably the single most influential in logic calculations)
2. Highway classification (toll roads, trunk, primary, seconday, tertiary, residential, service road et al)
3. Number of lanes
4. Maximum speed

GPS settings such as Ecoroute (fastest or most fuel efficient route) also count on this one for sometimes, the routes suggested by a GPS unit differs from Garmin Mapsource.

Anyone who can leave a definitive study on Garmin routing algorithm please leave a comment.

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