Open Water Breststrokes distance accuracy

Just tried an open water breaststrokes, while stroke count is good, distance accuracy is horrible at best.
I swam 2km (1km there and 1km back), ensuring I have good fix before start, ensure have good fix at the return point and again ensured I have good fix when returning to the starting position. This repeated twice as two activities.
I understand there will be weak if no GPS signal even few cm under the water while swimming with watch on the hand and don't expect to have tracking, but I would expect watch will be smart enough after getting fix to measure distance between two points with good fix with good accuracy while activity is running, but no.
Got 120 meters for first and 40 meters for second round logged in 2km swim. That's very disappointing.

Am I doing it wrong ?

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0 tmk2 over 8 years ago

... but I would expect watch will be smart enough after getting fix to measure distance between two points ...

I see your point, but that would require the watch to assume that the swimmer covered a straight line between those points and that is not a general case.

Am I doing it wrong ?

Well, yes. The watch needs GPS signal to accumulate distance. Breastroke won't work in open waters.

0 thigger over 8 years ago

If you're not doing a stroke where your arm comes out of the water, try sticking it under your hat.
Be aware that with the 910xt, if you left it in swim mode then even under your hat with a great view of the satellites it still only stored a point every few hundred metres. I'm not sure if the F5 will behave the same - if it does that you could try recording it as another activity type and changing it later.

0 Bit over 8 years ago

I get the distance from OW breaststroke swimming (with a Fenix 3) at the expense of time and speed accuracy: straight line to a turning point, then hold the watch above water, without pausing the activity. It then accumulates distance for up to 5 minutes. It takes a long time! You can see the distance increaae quickly at first and then slowly. The pace graph will be is totally off with this method.

Watch under swim cap works better, but I don't like wearing one in summer and I want to have stroke count.

If you have an old GPS watch lying around you can use that under a cap or on a swim buoy, to obtain a separate track recording.

0 tomulli over 8 years ago

I would argue, watch anyway needs to use valid fix points and some internal logic from sensors (maybe) to calculate distance and to make a path between two points, regardless what path is used.
In addition, most of the swimmers I know (talking about sport activity) are trying to swim in more or less straight line or combination of straight lines in open water.
Therefore it seems to me very irrational to not provide distance between two valid measured points if activity is running, regardless whether they are 1 or 100 meters far from each other.

Stroke count is more important to me as distance can be always measured somehow, so i can live with that however that will not prevent me to challenge used logic.
At least giving swimmer option in config menu would be great.

0 Bit over 8 years ago

Agreed. I was more or less expecting that the watch would do a kind of accelerometer-based dead reckoning (or reduced reckoning) distance and speed estimation between established GPS fixes. But it doesn't. Unfortunately I don't have a Fenix 5 (yet) and the Fenix 3 does not give the CIQ app programmer access to accelerometer data, otherwise that would be an area that I would explore.

The best thing would be a config option for the user so they can decide for themselves.

But in the mean time, let's hope that there are, or will be, app developers that will create an alternative swim app that does this. Or a data field.

0 wojtek_b over 8 years ago

I totally understand your needs, but IMHO swimming breaststroke with Fenix 5 is just like recording dog walks with it. It is a sport watch designed for triathlon, and no real triathlete swims breaststroke :) I don't want to say, whether you should or not swim breaststroke, but I wouldn't expect any changes from garmin to support it, as it is not what the watch is designed for, and probably won't be used by more then few people.

0 lustyd over 8 years ago

It is a sport watch designed for triathlon

No, the Forerunner 935 is a sport watch designed for triathlon. The Fenix range are outdoors watches (hiking etc.) which had triathlon retrofitted as an extra benefit along with a bunch of other features.
The OP has a very good point, if the watch knew it was at two points 1km apart there is no reason to log less than 2km under any circumstances. If it were drawing a wobbly line and adding distance that would be fine, but logging lower distance is weird. I'd be interested to see a screenshot of the track if you have it tomulli?
When I swim breaststroke I just life my watch arm every few strokes. It slows me down a bit but does get a good track. GPS reception is lost about 1cm down, you can test this before starting your activity as GPS drops on the screen as soon as you submerge. It comes back very quickly so I think a second every 10 strokes would do it to get you a track. with breast stroke your watch will be pointing at the sky so in theory is easier to get a fix when it surfaces.