Venture odometer vs. gps odometer

[gunkylump]

Beth and I completed a two week vacation on the bike a couple of weeks back. Still getting things put away and all that....it's boat loading season at work so not much time off to get things done.

 

The total kilometerage....how's that for a word? on the Venture odometer was 8,011 kilometers. The total on the zumo 550 that was on for every foot of the trip was 6,853.6. Now that's a difference of 1,157 kilometers, or 723 miles. WOW!

 

Thought I'd post this up....that's a pretty significant difference between the two.

 

Interesting food for thought.

 

gunk:scratchchin:

[LilBeaver]

Remember that the GPS only tracks your mileage (kilometer-age, lol)for when you have a signal [in addition to the unit being on]. Therefore, it is perfectly reasonable to expect the GPS to read less than the vehicle you are driving (in addition to the 1-2% offset the bike already has).

 

Hope you had a good trip!!

[V7Goose]

Yes, that is a huge difference, but there are a number of things that can cause it. For a difference that big, the most likely is time without a GPS signal.

 

There are three other main causes for distance discrepancies. First, the stock odometer is off by some % - it is not near as bad as the speedo, but still a bit optimistic - 1-3% typically.

 

Second, the GPS will have a trip setting somewhere that determines when it actually starts adding distance and time to the trip memory. Typically you can specify how fast and how far the machine must move before the GPS should assume you are actually traveling again (instead of maybe just moving around in a parking lot). Default setting may not actually be recording distance unless you are moving over 5 miles per hour.

 

The third cause is a bit harder to verify, but has to do with the frequency of position updates from the satellites. Position checks and distance calculations are not constant, but occur at discreet intervals, like pulses. The faster you travel, the more distance you will cover between each pulse. In a straight line, this makes no difference, but if you are in a sharp turn, the calculated distance will be a straight line between your actual position at each pulse, not the longer arc that you actually traveled. The difference may seem minuscule, but over many hours, days and miles all of those tiny differences can add up.

Goose