GPS swim distance isn't remotely accurate.

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Favorite Gear: Dimond | Cadex | Desoto Sport | Hoka One One

Then why do so many triathletes use a garmin 910xt??

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A false humanity is used to impose its opposite, by people whose cruelty is equalled only by their arrogance

explain please. Does romotely mean it could have only been about 350 yards or maybe as long as 7 miles? Your comment and judgement by their very nature demand more precision...

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Randy Christofferson(http://www.rcmioga.blogspot.com

Insert Doubt. Erase Hope. Crush Dreams.

I don't know for sure. I love mine and it has proven to be a very training device. It's expensive but has been well worth it to me. What prompts your question given the topic of the OP?

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Randy Christofferson(http://www.rcmioga.blogspot.com

Insert Doubt. Erase Hope. Crush Dreams.

the problem is simply that the gps fonction dont work under water. The 910xt will catch some data and extrapolate what distance it as done. it s not very accurate for many and for others with different swim style... it s much better.

I have a group of 25 swimmers in open water and we have use lots of 910xt and other device. It s a lottery.... not a great tool to rely on in the water. Once on land... it dosnt a much better job.

As for imc... if anything, the swim might have been a few meter short but for sure.... it wasnt long.

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Jonathan Caron / Professional Coach / ironman champions / age group world champions
Jonnyo Coaching
Instargram

Thanks Jon. Does anyone know what it's legit, tested accuracy is? I mean is it +/- 500% or +/- 5 % (like power meters) or some where in between....

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Randy Christofferson(http://www.rcmioga.blogspot.com

Insert Doubt. Erase Hope. Crush Dreams.

a swimmer like me with a high recovery....very text book stroke...i can get it within 2-3%

for a few of my swimmers, we have 10-20% error...

it s not the unit but also the swimmer/location of the watch etc that play a factor. So a % vary a lot from person to person.

the most reliable is to put it in your swim cap. And during swim practice, i follow the group on my surf board. The gps is on the board(dosnt go underwater) and accracy is within 1% error...like on a bike.

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Jonathan Caron / Professional Coach / ironman champions / age group world champions
Jonnyo Coaching
Instargram

I understand there is a degree of imprecision. That is why I asked the question. I figured a larger sample size would give me an idea of whether I navigated poorly. The 910 is reasonably accurate and consistent on my swims back home.

Anywho, just curious about other's results.

Scott

What jonnyo said.

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A false humanity is used to impose its opposite, by people whose cruelty is equalled only by their arrogance

Didn't wear my watch in the water but I took significantly longer than expected. I know I didn't have the best swim but it wasn't THAT bad either.

Here's what my Strava file looks like from a straight out-and-back swim (Garmin FR10 on wrist):



I may not be the world's straightest swimmer, but I'm not that bad.

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ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

I had my 310xt in my swim cap and I think it came up at 2.6 mi or so. Not sure if that was me swimming crooked. Will download my file when I get home and let me know. A few people I spoke with thought the swim was long fwiw.

Edit: My gps came out at 2.59 mi. My path looks pretty straight but me swimming an additional .19 seems fairly likely. I'd say this was probably the most accurate-distance Ironman swim course I've done.

Somewhere within the range of normal.

We had 7 people racing, 2 were a couple minutes faster than expected, myself and 2 others were about 1-2 minutes slower and 2 people were about normal. One guy had cramps and was a bit slower.

I swim about 1:01 to 1:05 depending on the day, I swam 1:04. I did hear that the T3 buoy may have drifted a bit because of wind on the second loop? Maybe… I was 29 min for lap 1 and then 35 min for lap 2 plus the finish, but that sounds about normal if you add in the extra 200m (i.e. lap 1 1800m, lap 2 plus finish 2000m)

The 2 people who had really great swims (i.e. PB but 2 min faster than expected) I encouraged to get in a more aggressive position at the start, closer to the buoy line, they complained about getting beat up a bit but both swam really well for their pool times…sometimes you have to get in the mix a bit ;-0

Positioning at the start would have a bit of an affect on what distance you swam. I would say within 100m of normal, or everyone I had racing was within 2 min of "expected". We use 10X400m LC pull set to determine what is "expected"

No way it was 600-700m long, that would mean that I am a sub 55 guy.

Maurice

I am guessing it was pretty accurate since its so simple a course and they have perminate 100 m markers out.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
http://Www.anthonytoth.ca, triathletetoth@twitter

Scott

The course was both designed and laid out using gps waypoints which were the same as last year. This gives exact locations for all turn buoys and ensures an accurate course, recreational gps units continually process information from satellites to provide the most accurate judgment of your movements in the environment you are in, swimming is the most inaccurate activity for these units. Of course it is possible you swam 4,600 meters too ;)

Best

Tim

Was your Garmin on your wrist or under the swim cap? How straight do you swim? Unless it was under the swim cap and you swim straight as an arrow it will always be "longer".

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Rodney
TrainingPeaks | Altra Running | RAD Roller
http://www.goinglong.ca

Really simple, look at the fastest swimmers, where they fast or slow? Seems like they may have been a tad fast, so tiny bit short course. You either swam long, slower than normal, or your gps mis read. Those are your options, so now pick the one you think most likely.