Marathon Tech Test: Apple vs. Garmin GPS Accuracy

The 2026 London Marathon provided a real-world test for two leading smartwatches: the Apple Watch Ultra 3 and the Garmin Forerunner 570. Both devices feature bright displays and dual-band GPS for enhanced tracking in difficult conditions.

During the marathon, both watches recorded distances remarkably close to the official 26.219 miles. The Apple Watch Ultra 3 logged 26.54 miles, while the Garmin Forerunner 570 recorded 26.57 miles. This slight overage is attributed to navigating crowds on the racecourse.

GPS performance was challenged in areas like Canary Wharf, known for its tall buildings, and the Blackfriars Underpass. In these spots, both watches showed a dip in pace accuracy, momentarily registering slower splits than the runner's consistent race pace. However, overall average paces were recorded at 7:55 min/mile for Apple and 7:54 min/mile for Garmin.

Heart rate monitoring was consistent, with both devices showing an average of 185 bpm and a max of 202 bpm. Usability was also a strong point, with both watches being easy to read in sunlight and familiar to use for experienced runners.

While the Garmin Forerunner 570 offers superior battery life, advanced training features, and a lower price point ($549 vs. $799), the Apple Watch Ultra 3 excels as a comprehensive smartwatch, offering seamless iPhone integration and features like responding to messages. Ultimately, both performed admirably, making the choice between them a matter of personal preference and ecosystem loyalty.