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Open water swimming - Garmin Forerunner 745 H E L P

4996798
over 3 years ago

My Garmin 745 is incredibly inaccurate over any distance when open water swimming.  EG today I did, possibly a 600yd swim and its registered 933.  Did a mile swim (1760 yards) and it registered over 2300 yards.  This is shocking.  Ive tried different satelites, just GPS and its still just at inaccurate.  Any tips.  I am a mostly a *** Stroke swimmer, but I do stop every so often to allow it to catch up, and if swimming long *** strokes, I tend to try and get the watch out the water.  

I just dont know what to do, the online help was more than useless.

  • 0 over 3 years ago

    I am not sure what *** stroke is, but if my guess if you are being censored is that your watch is under water most of the time. It only works for freestyle/back stroke, and perhaps butterfly if you don't have excessive glide. It should only need to catch up during turns and possibly the very end, and then be sure to push stop and save (I have forgotten on occasion until I am in the parking lot). It should be accurate to within +/- 10% (sadly).

  • 0 over 1 year ago

    I also have this issue. I have used the 745 for about 2 years now. Run and cycle GPS tracking is smooth and accurate. However, in the open sea it's way off. I compare with fellow swimmers on the same course/route and distances are in the difference by hundreds of meters. For example, a swim I did for 1600m, tracked by a few others, was recorded as 2100m for my watch.

    Has anyone found a solution or had success with software upgrades? 

  • 0 over 1 year ago in reply to 1309490

    Technologically, to date, it is an unsolvable problem.

    A Garmin cannot track your swim if you watch is underwater. They try to write software so it takes little snippets when your had is above water and tries to stitch together a reasonable assumption of your swim path/length.

    Imagine a watch coming into a position where it is able to latch onto a GPS satellite and grab a location reading, withing less than a second that the watch is up out of the water. Hundreds upon hundreds of little snippets.  Some strokes successfully work on getting a location reading, some didn't work, and the software has to stitch together whatever it has and make an estimate.

    Two things come into play.

    1) weird atmospheric/geologic conditions that make it hard to capture a GPS reading (in less than a second)

    2) The user swims in such a way that their watch stays out of the water an even shorter amount of time.  (.5 second?, breaststroke?)

    It is a G-D miracle that any watch can come up with any half way reasonable map/speed/distance of an OWS.

    I like open water swimming, and I would love a near perfect activity record of it.   Sometimes I conclude that my garmin did pretty well....other times it's hot garbage.