ER

I recently drove on NY State Thrughway (speed limit 65 mph). Throughout most of the trip my Navi was showing that I have 350 mi/4 hrs 48 min., then 300 mi/4 hrs. 10 min. to go, etc. essentially calculating my average speed to be 72-73 mph. Not that I drive within the speed limit, but how does my Navi know that? Anyone had the same experience?

Eugene

Slimey

The navi does have access to how fast your are traveling (GPS location traversed per unit time/speedometer/odometer/wheel speed...). It must average things out every few minutes or so. I think it also pays attention to the potential speed limits (or average driven speed) when it maps out for surface streets, highways, interstates, etc.

I've never seen any post concerning the actual algorithm, but maybe someone knows??? It's probably similar to the way mapquest will calculate average time on a mapping function.

Bladehunter

When you first enter your trip, (I'm guessing here) every road in the database has a weight which is a estimate of how fast it is to travel it. It uses this to calculate the quickest rout vs the shortest rout... It's probably more involved then this adding in speedlimit and distance needed to travel ext.....At it's simpilist form it probablly takes the distance needed to travel on the road and assumes you do the speedlimit to calculate time......