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Forerunner 935 accuracy on a track

bart_vdw
over 6 years ago
Today was the first day I used my Forerunner 935. I immediately tested it in two track races: a 3000m race and an 800m race:

* 3000m race: https://connect.garmin.com/modern/activity/1926043892
* 800m race: https://connect.garmin.com/modern/activity/1926043919

Notice that the distances recorded are not correct:
* 3000m race -> actual recorded distance is 3240m (240m extra, which is an error of 8%)
* 800m race -> actual recorded distance is 880m (80m extra, which is an error of 10%)

I have used the Virtual Partner in these races to set a pace, but because of the larger distances recorded, the pace given was too optimistic (which means I thought I was running at a good pace to break my record, but in reality I wasn't...).

Has anyone experienced errors of these magnitudes on track recordings? Can I do anything about it? Or might there be something wrong with my device?

Thanks for your comments,
Bart
  • 0 over 6 years ago
    Those are indeed the graphs i would like to see with my watch. However, I noticed that you are running software version 5.10.0.0. I wonder what would happen if you had 5.30.0.0 just as I have...


    Ah, indeed one of those is 5.10.0.0, but the other is 5.30.0.0 and just for completeness here another one I did yesterday with 5.33.0.0:

    https://connect.garmin.com/modern/activity/1946328802

  • 0 over 6 years ago
    I did another test today, and out of curiosity, I now put the watch on my left
    wrist. Test conditions were as follows:

    Clear blue sky
    Firmware version 5.30.0.0
    Constantly jogging in lane 1
    Forerunner 935 on my left wrist
    Ran 2 laps = 800m

    Resulting track:

    https://connect.garmin.com/modern/activity/1946721047

    Don't mind the third lap time and distance, I've pressed 'lap' instead of 'stop'
    at the end. But as you can see, the results are way better an much more
    acceptable than my first measurements: 400m for the first lap, 410m for the
    second lap.

    I'm still having a hard time believing that this is due to the left/right wrist
    thing. One important difference is the pace at which I was running: today, it
    was a slow jog (5:19 min/km) while for my other activities it was a race (3:48
    min/km). My educated guess is that it is more the running speed that
    influences the results rather than the left/right wrist thing. Maybe somehow
    the sattelite reception is harder at higher paces?

    I'll do more tests in the future, and post my results here. I'm still
    interested in comparisons between left/right wrist and different running
    speeds...


    Another thing could be location of the gps antenna... Not sure where it is put in the 935 but perhaps it has better exposure/reception when worn on the left hand as opposed to the right.
  • 0 over 6 years ago
    "If you are running on a track, the best option is a stopwatch" by Master Phillips....
    Absolutely agree, the distance is already 'certified'.
  • 0 over 6 years ago
    Another thing could be location of the gps antenna... Not sure where it is put in the 935 but perhaps it has better exposure/reception when worn on the left hand as opposed to the right.


    Interesting point in general. Can't say we have had any reports of this in any situation with the 935 however. With a 620 a few years ago, it seemed "better" on my right wrist say 9 out of 10 times just on regular runs. Never did figure that one out.
  • 0 over 6 years ago
    Ah, indeed one of those is 5.10.0.0, but the other is 5.30.0.0 and just for completeness here another one I did yesterday with 5.33.0.0:

    https://connect.garmin.com/modern/activity/1946328802



    Those are really nice heart rate graphs! Never seen such ones with my Forerunner 935 yet... I might try the upgrade to 5.33.0.0, but just to be sure: the heart rate in the above graph is *optical* heart rate measured on your wrist, right? Or did you wear a chest strap?
  • 0 over 6 years ago
    Those are really nice heart rate graphs! Never seen such ones with my Forerunner 935 yet... I might try the upgrade to 5.33.0.0, but just to be sure: the heart rate in the above graph is *optical* heart rate measured on your wrist, right? Or did you wear a chest strap?


    Just the OHR indeed... no chest wrap, to be honest I never had too many issues with OHR... it really depends on the person with OHR it seems.

    Also wrap it pretty tight (small wrists here, as tight as the one but latest hole). But yeah, I am indeed very happy with it :)
  • 0 over 6 years ago
    For your information: this weekend, I noticed that somewhere in the user settings, you can setup 'left wrist' or 'right wrist'. My watch was set to 'left wrist' and now I've changed it to 'right wrist'. I wonder whether that will improve my accuracy on a 400m track. I will keep you guys posted!

    Does anybody know if the 'left wrist' vs 'right wrist' user setting is actually *used* for something (accuracy of GPS reception or optical heart rate recording,...?) Or is it just some 'user profile setting' that one can configure but that currently is not yet really used...?
  • 0 over 6 years ago
    I may be wrong on this, but I think it might have something to do with the built-in accelerometer, which it uses to improve track accuracy
  • 0 over 6 years ago
    I think it's used for the "wrist gesture" feature, where turning your wrist can trigger the backlight. (The motion looks different from the watch's POV, depending on which wrist the watch is on.)
  • 0 over 6 years ago
    I think it's used for the "wrist gesture" feature, where turning your wrist can trigger the backlight. (The motion looks different from the watch's POV, depending on which wrist the watch is on.)


    Yes I think you are right and certainly logically more far likely than any GPS considerations.