GPS sprint trackers vs timing gates
GPS vests from Catapult and STATSports track how far and how fast you run in a match. For timing a short sprint they're the wrong tool, and the research on GPS accuracy backs that up.
What a GPS vest does
A GPS pod sits in a vest between your shoulder blades and logs your position from satellites, usually 10 times a second. Over a match or a practice, that adds up to total distance, high-speed running and your peak speed. Catapult One costs $179.99 a year, billed upfront, and the pod won't work without the membership. STATSports sells the Apex Athlete Series for about $299.99 with no subscription. Catapult says its consumer pod measures position to about 1 m.
Why GPS struggles with short sprints
A 10 m split takes under 2 seconds. At 10 samples a second and a meter or so of position error, the vest can't place the start or the 10 m line precisely enough to time it. Haugen and Buchheit's review of sprint monitoring found GPS validity acceptable only over distances longer than 30-40 m and for top speed, with typical errors of 3-15%. Error grows during hard acceleration, and the first 10 m of a sprint is all acceleration. GPS also needs open sky, so it fails indoors and gets worse in stadiums.
When to use which
A GPS vest is for games: how far you ran, how many sprints you made and your top speed in a match. Sprint testing needs a timing system, because you want the same distance and the same start every time, and hundredths of a second that mean something.
How Sprintbrick tracks position
Sprintbrick also tracks your position, but it uses a different radio and measures from a fixed point. A receiver sits behind your start and measures the distance to a sensor on your lower back 100 times a second using ultra-wideband radio, the kind phones use to find AirTags. We calibrated it against a tape out to 70 yards and the static error stayed within 4 cm.
When we ran it against OVR gates, every segment after the first 10 m came within 50 ms, 30 out of 30. The first 10 m is less settled, since it depends on when the clock starts, and we're still working on that. You give up range and direction: it measures straight runs away from the receiver, out to about 80 m, so it's a sprint testing tool and won't follow you around a soccer field.