Click images to ENLARGE.
My prior post from July 12, 2018.
Please refer to my July 12, 2018, post for background.
Garmin contacted me when I TWEETED about this and yesterday I sent them the information requested.
Today, I decided to check this out further and what I found totally disgusted me! The Garmin Fenix 5 ‘open swim’ distance measuring is a JOKE.
I ONLY swim the DOG-PADDLE so my Fenix 5 is always underwater. I appreciate that. But, per Garmin that is where the Fenix 5’s gyroscope kicks into help keep track of the distance.
So, this is what I found.
Invoked ‘Open Swim’ and waited until there was a GPS fix. I was basically walking up to my swimming depth while this was happening.
Then, with GPS active, pressed ‘START’, dove in and started swimming. Given it is in total 10-minutes, I must have swum 5-minutes to the swim platform. Grabbed the ladder and LIFTED my left arm, with the Fenix 5, out of the water.
The distance read 9 yards! There was no way that I had only smum 27′ (4.5 time my body length).
But, as I was holding the Fenix up, above the water, the distance started going up … LIKE CRAZY.
OK. So, that was good. The GPS was catching up.
It went … 19, 37, 50, 59, 65, 66 ….
All this time, I am totally stationary, holding onto the ladder. It is no longer funny.
So. I let go the ladder and start swimming back.
The swim back is a bit longer since I swim until there is not enough depth to swim.
Stood up. Looked at Fenix 5. It said 97 yards.
Then, immediately, 111 and then, as it had done at the swim platform, it kept on going.
I had enough. I hit STOP in disgust.
This is not funny.
‘Open Water Swim‘ is a BIG feature on the Fenix 5 — and it doesn’t work.
Don’t get me wrong. I am not a Garmin basher. I am actually a long-term Garmin shareholder!
Click images to ENLARGE.
Two Very Different GPS tracks for what is the SAME swim everyday!
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We have been at this lake for the last 11-years and my swim never varies. I start as close to head-on with the swim platform — when the water is waist deep. I then swim to the platform and back again — until I can’t swim any further because the water is too shallow. So, the top GPS track is accurate. I swim longer on the return leg — and it is possible, mainly due to wind, that my return leg is slightly ‘off course’ though I try to swim in a straight line using a marker on the beach for reference.
I have not as yet measured the distance, but I am fairly sure that the distance to/from the swim platform is more than 34 yards — per one of the readings. That would ~17 yards (51′) one-way. That would be the length of 2.5 twenty-foot boats. I know the swim is further than that.
Part of this has to be GPS accuracy. The distance here might be TOO SHORT for GPS to get a good handle. With Open Water Swimming the Fenix 5 uses GPS, the accelerometer and the gyroscope to estimate distance and movement. I noticed the other day that the distance jumped significantly after I had finished my swim and stood up.
I am not impressed.
The Vivoactive 3 and Forerunner 645, in particular, do NOT support ‘Open Water Swim’ though they do support ‘Pool Swim’.
This distinction and restriction drives folks nuts, so, I decided to get to the bottom of it.
It has all to do with GPS/Glonass support — or lack thereof IN WATER.
GPS does not work very well when the sensor is submerged in water. THAT IS THE CRUX OF THE ISSUE.
If you just want a GPS distance and track while you swim in open water you could try putting your watch into running mode and having it attached to a swim cap. That is supposed to work.
‘Pool Swim’, by definition, means that GPS is DISABLED. Pool swim data is measured using the ACCELEROMETER. Got that? No GPS … just accelerometer.
So, how do the more expensive watches like the Garmin Forerunner 935 and Fenix 5 support open water swimming? They use the GYROSCOPE.
With the gyroscope you only need occasional GPS fixes. The gyroscopes fills in the gaps between the GPS readings. The Vivoactive 3 does NOT have a gyroscope. Hence why open water swim is not available.
But, alas, a gyroscope alone is also NOT enough. For open water swim you ALSO need a powerful enough CPU to continually calculate the data. Got that?
Hence why open water swim is not supported on the Forerunner 645 though it has a gyroscope. The CPU in it is not as powerful as that in a FR935. Got that.
So, that is the deal.
To get open water swim support you need a gyroscope and a big enough CPU. Without that you only get pool swim which only uses the accelerometer.
You can TRY and use running or pool swim in open water — though the results will be mixed and most likely inaccurate.
So, that is the story. Now you know.