FR945 GPS Accuracy on a Running Track

No GPS watch will impress you on the track. GPS was never meant to do this and it always struggles there. Best way would bevor use a foot pod, calibrate it to the speed you want rotation in and use the pod for speed and distance on the track. Or use a fitting ConnectIQ App/Data Field  

By the way, lane 6 is the same length as lane 1 if you use the fitting lines. 

GPS struggles in the track but that looks worst than expected. I usually run in line 1 and mine says 0.25-0.26 miles, so too bad. 

With the exception of 1/4 of a lap (where it has wandered into some trees), this trace generally looks like the 3-5 m accuracy you would expect from GPS. Judging from the width of a 6 lane track, the radius of that one excursion is increased by 10-15m, so 30-50m of the overdistance is attributable to that.

but the level of inaccurary i will get, say, in a park will be more or less the same, right?

Actually I suspect even worse, since there will be trees and stuff..

What are fitting lanes?

When running in a park with longer straight distances, the watch algorithm uses the adjacent data points to "clean up" your heading and distance. While individual datapoints may be out, when you put a number of them together, the trend line becomes pretty clear and the errors can be discarded.

The problem with track running is that you are constantly turning and the straights are pretty short, which makes tracking distance a little harder for the watch.

Get a FR235 or FR735, then you will be impressed. They never disappoint me that the error rate is always lower than 0.5% on running track or an actual marathon race. However my FR945 always show 2-4% more than the actual distance.

Read again: lines, not lanes. If you use the curved start/stop line or the individual ones in the lanes, it is irrelevant wich lane you use, they are the all the same length

"By the way, lane 6 is the same length as lane 1 if you use the fitting lines"

he ran 4 laps, not only one!

if you like to have a more accurate distance use a foot pod like stryd

halfmarathon on the track (52 3/4 laps), stryd 21.11 km

connect.garmin.com/.../4891352312

Yep sorry.. I misspelled.. Anyways I understand now what you meant but yes as Uwe pointed out this would be feasible only if you run 400m..