FR945 swim map vs swim distance (GPS Issue)

I know that FR945 and Swim2 are different, with different HW and SW. However the basics of using the OW feature is the same. Cross-checking between different models is not uncommon, you can get very useful information from that. I regularly check FR45 (same HW as Swim2) and FR945 (same, or very similar SW for OW swim - remember, 945 received all the Swim2 functions in an update).

The fact, that all of your watch works well for OW is well known, you don't need to post more proof of that. I asked your routine before OW swim to be sure that I do not make any mistake.

Nico reported here the SAME issue than mine with his FR945. So the problem might be very similar. I reported my result to help him with his troubleshooting. I also hope to see his report, if he managed to resolve the issue, that might help me a lot.

Usually I post in the right thread, I know how to use this forum.

PG said:

I asked your routine before OW swim to be sure that I do not make any mistake.

I select the Open Water Swim activity and put the watch on the roof of my car while I put my wetsuit on. Once ready, put the watch on my wrist, down to the water, press start and swim. Nothing special really.

Thanks. Unfortunately after my watch was replaced, the issue still remained. I continue in the swim2 thread, and with the wrestling with Garmin Support. Either some special default settings are needed, or my front crawl is not suitable for these watches.

Nico, if you have some results, please comment, I would be happy to see some ideas what can go wrong 

Nothing special from my side other than what I wrote. This is from a particularly 'nasty' swim with some very rough water - just over 2min/100 from left to right then closer to 3:30/100 coming back from right to left. I'm would not class myself as a good swimmer. I have a stroke rate of around 30/min and can hit 2min/100m on a good day in the pool.

Playing around with settings such a PhysioTrue up is a red herring This is a post activity setting for syncing data between watches and has no impact on battery or processor use during an activity.

The reality is that there can be good days and bad days with GPS tracking; fortunately I have mostly good days with the occasional bad day. And this has been consistent since the 945 was released. Take a look back to the early posts in the 945 forum about open water swimming. Initially it was pretty poor but then got better after updates then occasionally poor before another update 'fixed it'. The main factor impacting swim recording is undoubtedly swim technique. Freestyle is the best stroke but you do need to have a reasonable technique. I'm a reasonable swimmer but I do have a low stroke rate of around 30/minute and a moving pace around 2:10/100m on a good day.

Satellites too move around so if you happen to have a day when they are close to the horizon you are likely to get a different result than if they all happen to be closer overhead. But that's true of all GPS activities. 

My settings have remained consistent throughout all my swimming - 1s recording, GPS+GLONASS, PhysioTrueUp on.

Simply put, there are many variables that affect the output for open water swimming. If you are continually having problems then contact Garmin Support as you might have a defective watch. If it keeps happening then the problem might well lie closer to home.

To illustrate: Swim yesterday with 945. Track suggests that it started recording some 200m offshore (I did start it before I got began swimming) yet distance and time was recorded throughout Overall distance is close to 500m further than it should be - known course of ~2500m,

Today's swim along a measured buoy line of 2000m. No problem although you could argue the track is not too flash it does reflect the overall path taken.

Your 2944m swim result is very consistent with my results from OWS whereby my FR 945 consistently over measures swim distance. I have documented this on this forum as well as reported to Garmin Tech support, yet the best response Garmin came up with through tech support was I don't swim in a straight line so I should expect over measurement. However 20-50% over actual distance is not reasonable. I only swim front crawl/freestyle. Others I swim with also have the FR945 and they experience the same problem. 

Philip - you commented on my swims 4 months ago: https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-945/212149/open-water-swim-fr945-settings


At one point Garmin suggested stop/start the watch every time I pause while swimming. This also yielded over measuring of the actual distance. 

I am so frustrated that I no longer use my FR945 for OWS. I use an Apple Watch 4, which is usually very accurate with the track as well as the distance measurement.

Your post has inspired me to try the FR 945 again for my swim in a few hours. I'll wear the Apple Watch as a back-up just in case  :-)

Very hopeful Garmin will fix this issue or someone on the forum has other insights on how to set the watch so I can return to using the 945 for OWS.

Just completed a swim, wearing both the FR945 and Apple watch 4. 

Garmin measured 2622 yards:  https://connect.garmin.com/modern/activity/4912317825
Apple Measured 1852 Yards

Apple was spot on for distance. Both watches were not quite perfect for the track, but I would not expect the track to be perfect. I swam on the land side of the wall heading towards the right and returned on the seaside of the wall when swimming to the left. It's very clear the Garmin did not capture any of the swim heading to the right along the wall.

I swam front crawl and floated a bit with the current on the way back.

Hoping Garmin Tech Support reads this thread!   

Apple Watch Track:

Garmin 945 Watch Track:

There at least was general issue, which Garmin has never said that they have fixed. Only improvements. Sony's chipset is good for battery life, bad for accuracy. 

https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-945/164018/945-appears-to-have-lost-gps-32-metres-into-open-water-swim

But situation is that philipshambrook says it works for him, Garmin hasn't said that they have fixed it, and it's still too cold for me to swim :) So I would like to see statement from Garmin saying that they have fixed it, or see on my own eyes that I won't be getting that anymore. We'll see, it's maybe swimmable in some weeks... now it's in one popular lake 11 degrees, that is too cold for my liking. 

I did some side-by-side testing with an AW4 last year and was impressed with the tracking in the open water. However, I did not see large discrepancies in the distance between the two watches.

I can honestly say that the swim the 945 recorded that was close to 500m long, even though it appeared to start tracking late, was an anomaly. The swims usually come in pretty close to 2000m allowing for tide and depending on how straight I swam.

Interestingly, I swam with an Instinct yesterday alongside the 945 and that stopped tracking about 200m offshore but carried on clocking up the time. That swim ended up being 200m light.