Fenix 6X : critical underestimation of the distance

Hello,

I know that several threads have already been written about that, but I want to emphasize.

I had the chance to run with 4 watches today (2 * 2 ) on what I think is a 13km run, and with 2 or 3 over the last days over other activities.

All the watches are fully up to date in terms of sofwares, set to GPS+Galileo, and for the F6x/s set to data recording every seconds.

The sattelites search has been done and left 'green' for 5 to 10 minutes without moving before starting for today run at least.

We are running mostly in the city (buildings).

Here are the results in km. I know that GPX overestimates structurally a bit the distance hence ratios below 100%.

GPX Read FIT Garmin  Ratio
F5 13,16 12,76 97,0%
F5X 13,08 12,89 98,5%
F6S 13,14 12,32 93,8%
F6X 13,24 12 90,6%

That was the first run for the 6S.

Absolutely the same run, a few days ago :

GPX Reader FIT Garmin  Ratio
F5 13,39 13,12 98,0%
F6X 13,08 12,26 93,7%

What I know to be a very close to a 10km run  :

GPX Reader FIT Garmin  Ratio
F5 10,7 10,2 95,3%
F5X 10,61 10,33 97,4%
F6X 10,07 9,25 91,9%

Curiously bike tracking is less crappy, but we are then leaving the city

GPX Reader FIT Garmin  Ratio
F5 53,52 52,36 97,8%
F6X 54 51,85 96,0%

It appears the at least the F6X is underestimating considerably the distance ran.

Furthermore the accuracy is really not good : in blue 6X, red 5X, I'm supposed to stay on the "Allée". 5X is pretty good there.

I'm should be seen on the "rue des vinaigriers" :

Has anyone been able to get a reply from Garmin on that issue ?

It is a bit a shame that we need to do this kind of analysis with what is supposed to be a top product.

Merci!

  • Bonjour,

    I gave another try by running with the 2 watches, 5X & 6X and for my partner the 6S.

    This is a close to 15km run, far from being ran for the first time.
    Garmin Basecamp manual drawing gives 15.1km so with a manual error of +/-1% let's say between 15.0 & 15.3 km.

    The speed & distance 3d have been deactivated on the 6X but not on the 5X (never had issues so far with these functionalities) and on the 6S (thus 6S is having them activated but not the 6X).

    The run is made within inner Paris, maybe with a bit less urban canyons than the previous 13km but not that much, within the city and then alongside the Seine and around the Eiffel Tower on the 'Field of Mars' which is more open.

    Here are the results :

    +/-1%
    Basecamp Manual Drawing 15,14 +/-0,15
    GPX FIT/Garmin Fit/Basecamp GPX/Basecamp Fit/GPX
    F5X 15,37 15,09 99,7% 101,5% 98,2%
    F6X 15,55 14,55 96,1% 102,7% 94,7%
    F6S 15,33 14,54 96,0% 101,3% 94,6%

    Interestingly the GPX are pretty the same for all, overestimating the distance, but no surprise, accuracy within urban canyons is complex.

    However the 5X is very accurate in terms of effective distance, 99.7% of the estimated distance, while both 6 X & S are not and are showing almost the same end results, lowered by around 0.5km. So still a 4% understimation where the 5X has almost none.

    The conclusion I would made is that given that the GPX are pretty the same, the GPS tracking is not the issue.

    I would say that  the software of the Fenix 6 is not yet precise enough. I hope that this is going to be enhanced.

    PS : so far no reply from Garmin on the email I made.

  • Unfortunately, V6 and actual gps firmware did not improve things. Made a 13.1 km trail through the woods and fenix 6 only came to 12.8 km. 

  • Well, I did two short runs today to test the accelerometer on a track, and the distance seems really fine. I was using my Samsung S10 to record too, and usually, it's better than the Garmin. The GPS distance of the Garmin was longer than the S10, not too surprising, since the GPS recording was not that great in the woods of Vincennes. But the "Garmin distance" seems to be spot on. I need to compared with longer runs like yours, but it's one of the rare times when I don't want to autocorrect the distance on Strava ! I don't think Garmin changed anything anyway, but it's not forbidden to hope ;)

  • So, being off by 300m after a 13.1km hike on a trail through the woods is unreasonable for you?

  • I think the problem is that in tougher conditions it is always shows a shorter distance.

    If it were well calibrated, it would sometimes show shorter, sometimes longer and mos of the time spot on (as it is in good conditions).

  • Bonjour,

    new test today on an almost exact 10km run with 3 watches (5X right & 6X left for me, 6S for my partner) with the new v6 software.

    Basically it is the same story : 5X appears to be very close from the realilty if not perfect (again) while 6 X & S underestimate by a non negligeable factor (7% and 6%).

    Estimated Distance : Garmin Basecamp Manual Drawing Measure
    10,0 +/-1% 9,9 10,1
    FIT Garmin GPX Ratio vs Estimated measure
    F5X 10,06 10,2 100,6%
    F6X 9,27 10,4 92,7%
    F6S 9,43 10,4 94,3%

    Once again the GPX are close on all the watches but the calculated distance by the F6 algo is underestimating.

    I had a reply form Garmin that I can simply translate by  "please reset the watche". I will try that but i wanted to test the neew software before to check.

    (

    in french even if I wrote to them in english

    • Eteindre la montre en maintenant le bouton « Light » (A peu près 5 secondes).
    • Maintenez le bouton « Haut Droit » + « Bas Droit » puis rallumez la montre avec le même bouton « Light » (3 boutons en même temps).
    • lâchez le bouton « Light »
    • Au premier Bip/Vibration, lâchez le bouton « Haut Droit »
    • Au deuxième Bip/Vibration, lâchez le bouton « Bas Droit »
    )
  • Your numbers are important and can't understand why some people are talking purely about GPS. 

    Your numbers reflect the effect of the smooth algorithm, probably a Kalman filter (I hope) on distance. 

    I am happy with my numbers even with wrong vo2max (for me the important is the vo2max variation not the absolute value) 

  • Hello O.Ret,

    how is your story goes on? I think you are absolutely right with your observations and conclusions. My friend had the same problem. He was always about -5% in wooded areas (btw he had 3D distance and 3D speed enabled). We both have Stryd (it is realy miraculous) now, so problems disappeared.....I am just curious if disabling 3D , new software or reset of the watch changed anything

    Best

  • @ - could you make a sample activity public and share the link here? Or, at least, making a screenshot of the elevation graph with superimposed pace on it - on the respective activity screen of GC Web, click the double-arrow symbol in the upper right corner of the elevation graph, and then, on the zoomed version of the graph, select the Pace Overlay in the uper right corner.

    From my experience, there are two principal problems with distance estimates:

    1. The first one being the 3D Distance feature (as already mentioned by ) - this is due to the limited accuracy of GPS-aquired elevation (in the order of tens of meters). It can introduce spikes and gaps in the elevation profile. However this would rather make the distance estimates longer, not shorter, as it seems to be in your case. Also, this is the case for watches with GPS aquired elevation, or with the auto-calibration enabled during the activity. Models with a baromteric altimeter and without the auto-calibration are rather "smoothing" the elevation curve, due to the hysteresis of the barometric sensors.

    2. And the second problem, that I have observed at some watch models, is detectable on the pace graph - when it includes gaps in the pace, the distance calculating algorithm on some watch models stops counting the distance within the gap. I assume that the gaps are caused by poor GPS connection. Some firmware versions ignore the gaps (smoothing them away), others exclude the sections from the distance calculation, what then leads to the underestimation of the total distance.

    You can, to certain extent, improve the quality of GPS reception, and the number of drop-outs by activating GPS+Glonass, or GPS+Galileo, and also using the "every second recording" GPS mode (attention - both of them will drain the battery little bit faster), but it will not completely eliminate the problem. I am unsure whether Garmin is aware of the problem, but for the moment you can't do more than using a 3rd party smoothing of the data (I think you can do so at Strava), or waiting for the firmware fix.

  • Bonjour,

    merci for your reply.

    For privacy reason I leave closed the activities.

    But see below some screenshots with the GPX.

    3d speed & distance are deactivated on the F6X (for 3 & 4 but not 2) but activated on the F5X for all of them.

    We can see more noise in the F6X & F6S vs F5X speed (Seine river lower bank zoomed : flat land, almost straight line, no obstacle, more open field)

    But more interesting it seems that there is a delay in the F6X & F6S. We can see our gradual acceleration with the green F5X line moving up. I'm terminating the acceleration faster than my partner hence the lower red 6S. But 5X & 6X should be the same level, they are and synchronous, which they are not.


    The pattern can be again found in the cadence for the same run (see the acceleration at the right)

    And the heart rate as well (Garmin chest HRM ANT+)

    The pattern is also found on other runs

    With an acceleration again :

    Another one