Trip Odometer Accuracy On Gecko 201/foretrex 101

[+LFlood]

I went on the same exact trailrun on two different days with my new Foretrex 101. I carefully reset the trip odometer before each run. The trip odometer readings were almost a full three-fourths of a mile difference for the same run!

 

There are some places along the run where the signal gets weak or non-existant due to tree cover. I have never had such a big discrepancy in my Meridian Platinum before, because I believe that it makes a straight line calculation to the next place when the signal gets strong again. Does anyone know for certain how Garmin deals with loss of signal along a track in terms of measuring trip distance?

 

I looked in the FAQ on their website and did not see it there. I have an e-mail in to them, but haven't even received an answer on the last e-mail.

[rickertk]

I believe the trip odometer stops measuring when signal is lost on the Garmins. I have a VistaC, and I've compared several bike rides to the bike computer (calibrated to wheel circumference). They've been within 1% on trip distance and average speed. Elevation gain (both the Vista C and my bike computer have barometric altimeters) has been a little more variant, but still probably within about 5-10% or so (which is the level of variation trip-to-trip on any one of them).

 

Keith

[peter]

With the original firmware I got with my Garmin eMap, the trip odometer would ignore any distance traveled without a signal lock. At some point the firmware was changed to now add in the straight-line distance as soon as signal lock is regained. I've noticed the odometer doing this on a few rides through dense redwood forests where the lock can be lost for a few tenths of a mile. The odometer then jumps up suddenly when lock is regained - still a slight underestimate since there may have been some curves along the way, but much better than dropping that distance completely.

 

Since the Foretrex is much newer I'd expect it to also incorporate the improved algorithm that adds the straight-line distance once the lock is regained. Have you checked how the tracklog looks for the two runs and compared the track lengths to the trip odometer readings?

[+LFlood]

That's what I'll do, I'll check tracklogs to see where the signal may have been lost. I'll also go somewhere I know the signal will be lost for while and look carefully at the trip odometer once the signal has been regained to see if it rapidly increases.

 

Thanks to both of you. The feedback is very helpful.