  Many runners use watches incorporating Global Positioning System technology
to track their workouts. These devices can be valuable training aids, but they
have limitations. For several reasons including variations in satellite
position, environmental factors, and design decisions made by the manufacturer,
GPS-enabled watches can produce position measurement errors. These can result
in incorrect estimations of total distance covered as well as running pace.
This study examined the accuracy of three Garmin running watches of different
technological generations using repetitive trials, over several years, by the
same runner over the same route. The older watches, a Forerunner 205 and a
Forerunner 220, showed similar accuracy when traversing the route. The newer
generation watch, a Forerunner 45S, was found to be significantly less accurate
in terms of both the trueness and precision of its distance measurements. This
may indicate that Garmin, in competition with other manufacturers of similar
devices, has chosen in recent years to prioritize device miniaturization and
battery life over accuracy.
