The Most Accurate GPS Watches! (Scientific Review)

Marathon GPS Watch Testing Overview00:00

A marathon was run with eight top-of-the-line watches to test GPS tracking performance: two Garmin watches, two Coros watches, two Suunto watches, and two Polar watches. The watches tested included the Garmin Forerunner 970 and Forerunner 570, Coros Pace Pro and Pace 4, Suunto Race 2 and Vertical 2, and Polar Vantage V3 and Grit X2 Pro. All watches were carried during the 42 km run on the same track in Vienna where Kipchoge ran his first unofficial sub-two-hour marathon.

Distance Measurements Recorded02:30

The total distance tracked varied between brands. Coros devices recorded approximately 43.33 km, Garmin recorded 42.4 km, Polar recorded roughly 42.7 km, Suunto Race 2 recorded 42.26 km, and Suunto Vertical 2 recorded 42.59 km. The average distance between Coros and Polar predictions was 400-500 m apart. The runner planned to run until all watches showed at least marathon distance plus 100-200 m wiggle room, ultimately running until Coros showed the lowest numbers.

GPS Signal Noise and Distance Discrepancies04:30

Polar watches showed more signal noise, with the Vantage V3 deviating significantly and the Grit X2 Pro running slightly ahead. This instability resulted in extra virtual meters added to total marathon distance. The increased distance could result from watch unreliability, suboptimal running lines, or differences in how marathon organizations measure distance.

Brand Consistency Analysis06:00

Within-brand consistency was measured by average distance between paired watches. Garmin and Coros showed 2 m average distance between their devices. Suunto and Polar, especially Polar, showed greater distances between their paired watches, indicating more signal noise.