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Incorrect OpenWater Swimming total distance and speed

scubajorgen
over 1 year ago

Issue

I did a comparison of the Fenix 7 with my TomTom Adventurer during open water swimming. It appeared that the distance logged by the Fenix (on the watch as well on Garmin Connect) was 2231 m whereas the distance logged by the TomTom was 3.16 km. I know from experience that the TomTom is right, hence the Fenix logged distance is to far to short (29% to short!!).

The speed recorded by the Fenix appears 2.37 min/100m which is 2.3 km/h which is also to low since I swim about 3.2 km/h. Makes sense, since the speed is derived from the distance.

Note that I attached both watches to my swimming buoy (20 cm distance between them) for better satellite signal reception. They were above water all the time with a clear 180/360 degree sky view.

Software version: 8.18

Analysis

Exporting both files to GPX (using own software tools) and showing the activities in Oziexporer reveals  some remarkable issues

In red the TomTom, in blue the Fenix.

Issues:

  • Some parts of the track do not contain trackpoints, revealing as straight lines. Especially in the northern part, which is the first part of swim and in the south-west corner.
  • Other parts of the track show trackpoints each second, whereas the Setting: Data Recording -> Frequency is set to 'Smart'. Usually it would skip trackpoints
  • Based on this, Oziexplorer reports a distance of 3.05 km for the Fenix, which confirms the 2231 m of the Fenix/Garmin Connect is far to low.

I enclose the original FIT file of the activity: tracklog.studioblueplanet.net/2022-05-17-19-43-02.fit

On close analysis the FIT file contains 1053 erronous [lat, lon] coordinates [180, 180]. This cannot be due to poor satellite reception since the watch was on top of the buoy giving it a 180 degrees sky view 360 degrees around (the best you can get). 

Note that in the conversion to GPX format, I filtered the [180, 180] coordinates out.

The GPX contains 2448 correct coordinates. Assuming each coordinate represents the same distance and a wrong coordinate is not counted in the total distance, this would mean the total distance calculated is 2448/(2448+1053) * 3.16 km =  2209 m, which is pretty close to the reported 2231 m by the Fenix and Garmin Connect.

I checked another Open water Swimming activity in which I compared the TomTom (on buoy) and Fenix 7 (on wrist).

TomTom (blue): 2.17 km

Fenix (red): 2.06 km, 17 malformed [180, 180] lat/lon coordinates

I checked a trail run: 1 malformed [180, 180] coordinate

I checked a generic cycling event: 0 malformed coordinates

I checked a short hike: 1 malformed coordinate

Conclusion

  • The Fenix logs wrong coordinates [180, 180] in all activities. 
    In Open Water Swimming they appear to be numerous. 
  • Calculation suggests that this results in wrong distance calculations on the Fenix, which renders the watch not very usable for the serious sporter!!
    Other posts on this forum also report wrong total distance for other activities.

Advice:

  • Solve the bugs so coordinates are correctly logged
  • Make sure that if occasionally a wrong coordinate occurs, it is omitted for distance calculation. In other words calculate the distance only by calculating the distance between correct coordinates. This gives better results than current situation.
  • 0 over 1 year ago in reply to 5793390

    It should do as the watch will likely have a constant connection to the satellites.

  • 0 over 1 year ago in reply to philipshambrook

    As we can see, it works only for you.

  • 0 over 1 year ago in reply to philipshambrook

    A potentially stupid, non-rhetorical question.... if this is a software problem, how come it works for some people? How do you get it to work for you?

  • 0 over 1 year ago in reply to DanielR1972
    DanielR1972 said:
    How do you get it to work for you?

    I just swim freestyle. Nothing fancy. No real thought to it. I just swim.

    The discussions about this are plentiful across different watches ever since the 310XT. It might pay to read through some of them. Suffice it to say, if there is nothing wrong with the watch then it leaves only two possibilities, the software or the swimmer. So, since the software is likely to be common to all that leaves the swimmer. My recommendation is, and always has been, that if a problem persists that Garmin Support is contacted. Working with them will bring a solution closer for those who are having problems recording open water swims, hopefully without breaking it for those for whom it works. 

  • 0 over 1 year ago in reply to philipshambrook

    I did, but response is slow. Since it doesn‘t work for some (not knowing what magic moves you can apply to freestyle), I‘m thinking to send it in. Due to warranty one may come to the point that seller/garmin has to take the watch back. OWS is during summer season an important part of my workout, and that this new watch is obviously not capable of doing that (for some), and that Garmin is not really responsive, I guess this is the only way to treat this issue.

  • 0 over 1 year ago in reply to Hexa1962

    I must also swim in a way that Garmin doesn't think is appropriate. So shall also return.

  • 0 over 1 year ago in reply to DanielR1972

    Garmin and CEO of garmin, i can’t believe that it’s so many problems with open water swimming!! today and the same yesterday totally wrong distance and pace!! I’m the owner of many garmin devices, bJoy very disappointed with fenix7!! first there was problems with swimming in pool but now with opws totally disaster!! my pace is now on2.15..no go!!

    garmin doing something or old customers will leave you after many years!!!!!!!!!

  • 0 over 1 year ago in reply to renton82

    Yes that's true. Of all the thousands upon thousands of Fenix 7/Fenix 6 etc watches sold, I'm the only one who manages to consistently show good open water swim results. Clearly I must be faking it.

    BTW, have you actually swam in the open water with your Fenix 7 yet? All we've seen is continual carping from you without any evidence that you've been in the water.

    PS

    I voted your reply up so people could see how ridiculous the comment was!

  • 0 over 1 year ago in reply to DanielR1972

    I truly am sorry you feel that way. However, the way to a successful resolution is to work with Garmin Support to find a solution. There have been many adjustments to the swim algorithms over the years since the 310XT, resulting in what I believe to be more people with fewer problems recording open water swims. The more data Garmin has the better the chance of finding something that work for everyone.

  • 0 over 1 year ago

    Definetly something happens with the Fenix under reporting distance in OW. In 2000 meters activity loss around 300/400 m less, so pace is also lower than it should be. I checked it in a race and also exporting the track to google earth and measuring following the track exported. My watch is a F6.

    Today i swim with a colleage. I wear the F6x and he is wearing a swim 2. We were in parallel during all the track. We know the track is 3000m. In Garmin connect he reported correctly 3000 m, mine was 2600m. On the watch when we finished he has 3200m on the swim 2, my f6x was 2600. Seems that Garmin connect modified to the correct lenght for the swim 2 but not for my fenix 6x, also the f6x suffered a big gap off for the distance on the watch than the swim2. Please is someone from Garmin could report this issue.