Forerunner 935 accuracy on a track

Which wrist were you wearing your 935 - left or right? Very important to wear on the left on a track.

Haven't done a huge amount of track running with a 935 but when I did it was pretty good.
https://connect.garmin.com/modern/activity/1807498926 was some test run I was doing. Looks like I ran 9 laps and 1 straight so 3700m it is comes up 2.31 miles which is 3718 metres. So pretty good indeed :)

Which wrist were you wearing your 935 - left or right? Very important to wear on the left on a track.

I had it on my right wrist. But why would that be very important???

When on a track I work my time out per lap and then manual lap and check my lap time, seems to be the easiest way and you are not reliant on GPS then.

I had it on my right wrist. But why would that be very important???

Well for a start if it is on your right wrist your watch is almost in lane 2 and running in lane 2 adds about 7.5 metres per lap.

Secondly there has been bit of a bit of a problem with Garmins over the years where wearing it on your right wrist seems to add a lot more distance than just the width of yourself.
I have done track runs with watches on both wrists where the one on the left was fine but the one on the right wrist was almost a lap long in a 5K - which is similar to what you are seeing.

Try it on left wrist next time and see if any better.

Well for a start if it is on your right wrist your watch is almost in lane 2 and running in lane 2 adds about 7.5 metres per lap.

I understand that, but for my 3000m race I had to run 7,5 laps, which would add about 7.5 x 7.5 = 56,35 metres. My Forerunner 935 recorded 240 meters more! I believe this cannot be attributed only to the difference left/right wrist.

Also, for my 800m race, I started in lane 3. That start position seems to be quite accurate in the track log at https://connect.garmin.com/modern/activity/1926043919 After the first turn, I almost continuously ran in lane 1, but this is not what I see in my recorded track. The recorded track seems to indicate that I ran in the outer lanes, and in the curved parts even outside the track! These incorrect track points are of course the reason why I have recorded 80 metres more. I wonder why it is only the start position that is quite accurate, but once I started running, it looks like the recorded track points are a few meters more to the 'outside' of what I was running... I wonder why that is...

This is not the first time that discussions about the accuracy of any GPS device on the track have arisen. Like it or not, those margins of error you have recorded are not unreasonable.

There are many posts dotted throughout the forum about this very subject over many years and involving most of the GPS devices Garmin produces. I would not expect it to be any different for any other GPS device. What it boils down to is that portable GPS fitness devices are not suited for running on the track if you require pinpoint accuracy. The margin of error is too large. It's not really what these devices are designed for. If you are running on a track, the best option is a stopwatch.

I've never had any Garmin watch record properly on a track. I turn off auto-lap as the 1 mile marker would go off well before a mile.
That being said, I've been using the Stryd footpod for distance and pace.

https://connect.garmin.com/modern/activity/1878869259

You don't get much more accurate then that.

> If you are running on a track, the best option is a stopwatch.
This is very true. If you are doing a track race work out what your 400 splits should be and check how you are doing end of each lap. All the track races I have ever done (and that is hundreds) then they even call out splits so in reality you don't need any watch yourself although of course like to record it for Strava etc etc

Yesterday, I ran a 5000m race (in 18:58.19):

https://connect.garmin.com/modern/activity/1941142234

Again, I am *very* disappointed by the error in the distance of the recorded track. I edited the summary information of the above activity to the correct distance and time, but if you look at the graphs below (set to 'Over Distance'), you can see that a distance of 5490m was recorded. Had it recorded 5050m or so, I would find this acceptable, but my device recorded 5490m instead of 5000m... That is an error of 10%!!! In the meanwhile, I know that garmin sportwatches on a 400m track are less accurate than on the road, but an error of 10% is quite unacceptable for a 550 EUR device if you ask me... I never had this magnitude of errors with my Garmin Forerunner 305 on a 400m track. And how can I be sure that the error is also not 10% when running on the road??? Should I consider my Forerunner 935 as defective and return it? Or is this normal behavior?

I had very bad results with 910XT but with F3 and also 935 I have only minor discrepancy when running on the track. For 400m rounds, it is about 2-3 meters and sums up to say 10m per 1000m. Distance is always longer on the 935 than in reality. This is sufficient for my workouts.

But as Tim stated, the best is to use a standard stop watch and lap every 200 or 400m.