Related
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Open water swimming

9603233
over 3 years ago

A new Garmin 935 has measured my 1st open water swim incorrectly. It has measured a distance that is probably 30% of the distance actually swum. Please can you let me know what can be done about this and how the error can rectified. Very frustrating for a top of the range triathlon watch !

  • 0 9 months ago

    I swim 400 meter lengths, and I can get accurate total length of my workout (1600 meters) if I wait for the GPS to "catch up" at each end with my wrist out of the water.  Even then, the map view of the workout is all over the place.  If I do not wait, its no wonder the length reads inaccurate because a point is not always captured right where I turn around.  I have tried waiting just long enough for the map view to update my position after finishing a length (I can at least see I am at the correct end of my previous traces), however this is not good enough--the algorithm must be discarding the end of the length as an outlier (which makes sense I suppose).  You need a minute at the end of the length so it can record the endpoint with confidence. 

    Has anyone upgraded to a newer Forerunner and had better luck?

  • 0 9 months ago in reply to 4680732

    I find the 945LTE (and my wife's Fenix 6s) both seem to plot more data points and follow an actual swim course better when it includes random wiggles/turns and what-not.

    Examples -

    I often swim faster than my wife and end up randomly looping back past her before resuming on our "out and back" course.  I have done this fairly consistently for roughly the past ~4 years - some of which with a 935 and then with a 945LTE since launch.  For scale/reference the below lake is about 700-750 yds (~650m) straight across.

    The 935 would often look like these:

    The 945LTE looks like this:

    Note, the above include intentional swims that aren't quite out and back (off to the left and then back on track) but I think you can see some of the difference in the track recorded.  The provided 945LTE picture includes a circle back about halfway and then a "wiggle" as I approached my turn around.  I am guessing the "wiggle" would have been totally missed / aliased away with my old 935 from a few years ago.

    Around the time I had the 935 I would also swim with a second watch or phone in my safety buoy which could provide more accurate numbers.  In general with my routes and method of swimming the 935 was ~10-20% short on distance while the 945LTE showed very close to reference distance - I have not done the test again lately as I am generally trusting the recording and the tracks look realistic.

    I anticipate / expect the newer dual-band watches would perform even better yet, but I have not researched it or tried it myself.