Open water distance

done a 70.3 triathlon two days ago, 1.9km swim was recorded as 1.815km, track recorded looks very smooth and good. i am used to have a good "gps soaking" before start, by opening the activity well before start. fw 15.09 beta.

I always open the activity when I put back the watch after the wet-suit. I still have to finish dressing, load the buy with drinks, and walk to the water: so plenty of "soak" time...

The track looks very good. I just changed smart to every second tracking, to see if it improves accuracy.

Going to load & check more tracks when I have time.

as far as i know, Open Water Swim activity do not change its GPS/GNSS behavior even if the system is set to record every second. my general settings are "smart recording" but fw15.09 recorded my swim every second nonetheless

8.9km is impressive. The error could be in the transfer process or Google maps. My experience is similar to OperationOne measuring <4% error compared to another watch attached to my swim buoy (GPS settings at All + multiband).. I know that seems like a lot, but dcrainmaker suggested a few years ago that 10% error was considered the norm for open water swimming. For OW, the watch is under water where it cannot get a signal for a considerable portion of time. Thus it uses an algorithm to estimate what happens then. People have differences in stroke, speed consistency etc. OperationOne note that race courses are sometimes not exact (which is why there are no official world records for OW distances). They can be affected by buoy movement with wind, tides altering the start/finish, and human measurement error marking the course. So probably not what you want to hear, but if you want to be 100% accurate, you need to put he watch on a buoy or in your cap. I'm pretty happy with the small error.

I don't worry about small errors, after all I swim for my pleasure. A 20% error is a LOT! I keep tabs on distances so I don't get too greedy. On a round swim, even feeling very good, at 4-5km I have to turn back, or get cold and struggle by the end.

The track is pretty clean, but I'll put the watch on the buoy to try out if distance is more accurate compared to google earth. O maybe is google earth providing the wrong distance?

I've checked other tracks and most disagree with google earth, only a couple shorter swims in the 1km range match quite well. I rarely do short swims, most are in the 4-5km (garmin distance). I'd like to do more 10km, but rarely find the 3h required.

Interesting results as it has been usually just the opposite and the OWS is missing distance. Well, it's still month or two to get the OWS season opened here, so can see has they fixed anything during the winter.

Can someone test the following:

• In Garmin Connect, export a long open water swim as a .gpx
• Import the same track back in to Garmin connect.
• Compare recorded distance to track length.

In my case the watch records a staggering +24% distance. The imported track matches a .gpx export to google earth, and follows perfectly the swim, around the rocky coast, or rounding small islands, so I know it is very accurate.

Since the track is perfect, this is not due to the GPS signal being broken while the watch is underwater. If you connect all the recorded points in a track (GPS), the resulting distance is perfect.

Tried the same with run tracks, and the recorded distance matches the imported track.

So the 955 is definitely doing weird and completely wrong swimming calculations not related to GPS tracking.

But granted, they said 5 months ago, that the issue should be fixed. Your experience given pretty much different picture.
My experience will still need to wait month or two... 

Thanks a lot for your return.

Is there current in that fresh water swim? 3m per stroke is huge!

I get "not the swim season": the water is probably not the right consistency LOL