1. High-accuracy location request. LapSector uses the browser Geolocation API with enableHighAccuracy: true, zero cached-position age and a continuous watchPosition() stream.

2. Adaptive position filter. Each accepted fix is converted to local metre coordinates. A velocity-aware alpha-beta style filter predicts the next position and then corrects that prediction using the new GPS measurement. Better accuracy receives more weight; noisy fixes receive less.

3. Jump rejection. A fix that would require an implausible movement compared with the previous motion, elapsed time and reported GPS uncertainty is ignored instead of creating a false trail or false gate crossing.

4. Speed fusion. When the phone supplies native GPS speed, LapSector blends it with speed calculated from position movement. If native speed is missing, movement-derived speed is used.

5. Dual-path gate crossing. The timing engine checks both stabilized coordinates and the original raw GPS coordinates. When both produce a valid crossing, the crossing fraction is accuracy-weighted to preserve responsiveness without letting jitter dominate.

6. Accuracy-aware gate corridor. The start/sector line gets a small virtual end tolerance based on GPS uncertainty. This helps prevent a valid crossing from being missed because the reported position was a few metres sideways. It does not move the car onto the track.

7. Sub-sample timestamp interpolation. LapSector does not simply use the time of the first GPS point after the line. It calculates where between the previous and current samples the crossing happened and interpolates the timestamp to that fraction of the interval.

The displayed GPS accuracy value is the phone/browser estimate in metres, not a guarantee. A typical phone may report roughly 3–10 m in good open-sky conditions, and the update rate is controlled by the device and browser.

LapSector can improve stability and crossing-time estimation, but it cannot access carrier-phase GNSS, RTK corrections or raw high-rate satellite measurements through ordinary browser Geolocation. For professional sub-metre or centimetre timing, external GNSS hardware or a native integration is required.

• Mount the phone securely with a clear view of the sky; avoid placing it deep under a metal roof or dashboard.
• Enable Precise Location for the browser/PWA. On Android, also use the highest available location accuracy.
• Open LapSector outdoors before the session and give the phone time to obtain a stable fix.
• Prefer an installed PWA or the normal browser with the screen active. Battery-saving modes can reduce location update frequency.
• Do not switch apps or lock the phone during a timed session if your device suspends browser location in the background.
• For the cleanest comparison between laps, use the same phone and mounting position for the whole session.

Find the circuit: in Build, use “Find track or place” to search for a circuit name, town, small village, address or latitude/longitude. Choosing a result only moves the map; it never changes your saved gates.

Start / Finish: draw the line from one side of the track to the other. Make it slightly wider than the driven surface so normal GPS lateral error cannot miss the line.

Checkpoints: add them in driving order. LapSector expects each checkpoint before it allows the finish line to complete that lap.

Placement: avoid putting timing lines directly inside very tight hairpins or places where two sections of track run extremely close together. A straighter crossing gives the most stable timing geometry.

Editing: only the track owner can edit their track. Saving updates the track definition used by future sessions.

Custom/private tracks: choose Custom before saving to keep the track out of the public Track Library. It stays attached to your account under My tracks.

Sharing a custom track: open your custom track and press Share private track. Anyone who opens that link and signs in gets the track added to My tracks. They can drive it and see later owner updates, but only the owner can edit the original.

Main timer: starts when you cross Start / Finish. Crossing it again after all required checkpoints completes the lap.

S1, S2, S3…: sector times are calculated from cumulative checkpoint timestamps.

Lap prediction: compares your current progress with the previous/reference lap and estimates whether the current lap is faster or slower.

Follow car: keeps the map centred on your current position. “Show whole track” returns to a fixed overview.

GPS quality: uses the accuracy estimate delivered by the phone. Lower metres are better.

During a real GPS session LapSector shares your public driver name, selected car, position and live timing with the live view for that track. Sharing stops when you press Stop Session.

Other users can open the track, see active drivers on the satellite map, view current timing and follow a selected live car. Your sign-in email is not shown on the public leaderboard or live map.

The Top 100 stores the fastest valid real GPS lap for each driver/car combination on a track. The same driver can therefore appear more than once when using different cars.

Simulation is for testing track geometry and the timing flow. Simulated laps are intentionally excluded from the public Top 100.

Completed laps can store the GPS samples needed to compare full-lap traces. The analysis view can compare Lap A and Lap B by driving distance and show speed, altitude, acceleration and GPS accuracy with checkpoint markers.

Phone GPS cannot provide engine RPM, throttle position or gear by itself. Those channels require a future OBD/CAN or external sensor connection.

No signal: check browser location permission, Precise Location and that system Location Services are enabled.

Position jumps: move outdoors, wait for accuracy to improve and disable aggressive battery saving. LapSector filters implausible jumps, but severe multipath near buildings/metal structures can still degrade GPS.

Lap does not start: confirm the Start / Finish line spans the track and that GPS accuracy is reasonable.

Lap does not finish: all checkpoints must be crossed in their saved order before Start / Finish can complete the lap.

Timing looks inconsistent: compare the GPS accuracy graph in Telemetry. Large accuracy changes usually indicate the phone's GNSS solution, not the stopwatch display.

LapSector is a Progressive Web App (PWA). On supported devices, use the Install prompt or add the site to the Home Screen. The app shell is cached for faster startup, while live tracks, accounts and timing data still use the server when required.

Automatic updates: LapSector checks the server when the app starts, whenever it returns to the foreground and every 60 seconds while it is open. If a newer build is available it reloads automatically when it is safe. An active timing session is never interrupted; the update waits until you press Stop Session. Unsaved track editing is also protected and the update waits until the track has been saved or you leave the edit safely.