How to Record Perfect GPS Laps for Racing
Published: August 2026 · 5 min read
Whether you are running track repeats, doing hot laps at a karting circuit, or riding criteriums, clean GPS lap data is the foundation of good analysis. When your recording is noisy or inconsistent, lap-detection tools struggle, and you end up with wrong lap counts and inaccurate times. Here is how to get it right.
1. Use the right recording mode
Most modern GPS devices offer a lap-button mode. This is the gold standard for circuit work. Press the lap button exactly at the start/finish line each lap, and your device writes a clean lap marker into the file. The Lap Detector in GPX Tools can then split on these markers with 100% accuracy.
If you cannot use a lap button — for example, you are recording on a GoPro, a drone, or a basic smartphone app — you need the automatic detection mode. This algorithm finds start/finish crossings by proximity. The cleaner your GPS trace, the better it works.
2. Set your GPS to 1-second recording
Most devices default to "smart recording" which varies the recording interval based on speed and direction changes. While this saves battery and storage, it introduces gaps — sometimes several seconds — between points. For lap detection, every second counts. Set your device to record at a fixed 1-second interval. With 1-second data, two consecutive points near the start/finish line are only a few metres apart, making the proximity detection precise.
3. Do a complete out-lap before your first timed lap
If your recording starts at the pit exit or somewhere on track that is not the start/finish line, your first "lap" in the data file will be a partial out-lap. This is fine — the Lap Detector flags partial trailing laps. But ideally: start your recording 10—20 metres before the start/finish line, cross it, and then begin your first full lap. This ensures lap 1 in your data is a complete circuit.
4. Avoid GPS signal loss near the start/finish
If the start/finish is under a bridge, inside a tunnel, or in a dense urban canyon, GPS accuracy drops and the proximity algorithm may miss a crossing or generate a false positive. In these cases, increase the capture radius in the Lap Detector (e.g. from 20 m to 40 m) and set a minimum lap-time guard (e.g. 30 seconds) to reject spurious triggers.
5. Close your laps properly
A "closed loop" means the last point of the lap is near the first point. If you stop recording mid-circuit, the last lap is partial and the file ends abruptly. For the Lap Replicator to work well (dropping the seam between laps), the source lap should end within about 15 metres of where it started. Walk or ride all the way back to the line.
Already have a recording? Drop it into GPX Tools and use the Lap Detector to split it into per-lap segments.
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