Track Log Distance vs Trip Odometer Distance

[iQueRMA]

Has anyone tried comparing the distance measured in the track log versus the trip odometer? I had reset all the trip readings and cleared the track log then took a walk for several miles. In the end the two distances did not match. I tried this a couple of times and each time the trip odometer distance was higher. Anyone have a clue why? I emailed Garmin with this question but haven't heard back yet.

[TWN]

This makes sense when you think how the two functions measure distance. The track log is a series of points recorded on you journey and the distance using the track log is measured form a series of STRAIGHT LINES between these points. The Trip Odometer measures distance each time the gps processor calculates your location from the stateliest. I'm not sure how often the 3600 calculates location but the typical gps does it about once a second and less often in battery saver mode. When you calculate the distance in smaller straight line increments, you get a more accurate [longer] distance. Increasing the frequency of recorded track points will give better distance accuracy.
Hope this helps..........T

[JMckie]

I analyzed this in detail in this thread. See post #10

http://www.pdastreet.com/forums/showthread.php?t=57319&page=1&pp=15

These are the different sampling frequencies:
Birdwatch - once every second
QueTracks - every 22 seconds (track frequency set to highest setting)
QueTrip - guess: every 30 seconds?
PathAway - every 70 seconds

[iQueRMA]

Thanks TWN and JMckie for your responses. I didn't think about the different sampling rates for the track log versus the trip odometer. I have my track interval set to normal which I assume is a lower sampling rate than the trip odometer. I guess that's why my trip odometer is higher than the track log.

[iQueRMA]

FYI, I set the track interval to most often and took a walk. Track log 1.92 miles vs 1.94 miles on the trip odometer. Thanks for the tip JMckie.

[JMckie]

You're welcome.

Also if you look at the thread I linked to (post #10), I attached a picture there illustrating the discrepancy. If you were travelling in a straight line, it doesn't matter what the sampling rate is, you will get exactly the same distance. It's when you are changing directions frequently as in a hiking trail where the differences get more noticeable.