Start test: open Start to run a standing-start acceleration test with five red lights. The lights illuminate one by one, all five remain on briefly, then go out after a randomized delay. Timing starts at lights-out.

20 / 30 / 40 / 50 m or custom distance: choose a preset or enter your own distance. When a longer test is selected, intermediate split distances are recorded when available.

Launch RPM + car comparison: enter the launch RPM, save the result to your own account with the car used, then select previous starts to compare elapsed times and the RPM-versus-time trend.

Android Native GPS: the downloadable Android app loads the same LapSector service, login and database, while replacing navigator.geolocation with Android FusedLocationProvider data inside the app.

New navigation: desktop uses the full centred bottom dock. On phones the normal view uses larger Home, Drive, Start and Menu buttons; Menu expands the complete navigation.

Pocket Lock: during a real GPS session you can lock the controls to prevent accidental taps. Auto Pocket Lock can lock them automatically after the session starts; hold the unlock control for three seconds to unlock.

Pro Telemetry: Pro analysis can compare laps and drivers by track position with speed, time delta, sectors, racing-line comparison and GPS-derived performance data.

Pro test mode: the administrator can switch the account between FREE and PRO in Account to test the paid-version lock before Stripe payments are enabled.

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. On an existing track, open Edit track / racing line and hold-drag either endpoint to resize or rotate the saved line.

Checkpoints: add them in driving order. LapSector expects each checkpoint before it allows the finish line to complete that lap. Existing checkpoints can be resized or rotated by hold-dragging either endpoint; the new length is shown live while dragging.

Racing line (optional): press Draw racing line and drag your mouse or finger continuously around the intended driving line in the direction of travel. This reference line is used by Simulate This Track and can be overlaid in Pro Telemetry. It is never generated automatically.

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.

1. Stop the car. Open Start, choose 20, 30, 40, 50 m or enter a custom distance.

2. Enter launch RPM. This is optional while setting up, but recommended if you want to determine which launch RPM produces the fastest start.

3. Start the light sequence. Five red lights illuminate one at a time. After all five are illuminated, they go out after a randomized delay. The stopwatch starts at the exact lights-out timestamp — not when the car first moves.

4. Drive through the selected distance. LapSector measures travelled GPS distance from the start position and interpolates the target-distance crossing between the surrounding GPS samples instead of rounding the result to the next whole GPS fix.

5. Save the run. Select the car used and confirm the launch RPM. The run is saved to your signed-in account with elapsed time, splits, GPS samples, speed and GPS accuracy.

6. Compare starts. Select saved runs at the same comparison distance to compare cars and setups. The launch-RPM chart plots RPM against elapsed time so repeated tests can reveal which RPM range works best.

Fair comparisons: compare tests on the same distance and, where possible, the same surface, direction, tyres and conditions. GPS-based acceleration testing is useful for setup trends but is not a substitute for professional drag timing equipment.

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.

Desktop: the complete Home, Drive, Start, Tracks, Sessions, Build and Help dock is centred at the bottom of the app.

Phone: the compact dock shows larger Home, Drive, Start and Menu controls. Tap Menu to expand all navigation choices; selecting a view closes the expanded menu automatically.

Pocket Lock: use Lock controls during a real timing session if the mounted phone can be touched accidentally. With Auto Pocket Lock enabled, LapSector locks the controls five seconds after the real GPS session starts while keeping the timing display visible. Hold the unlock control for three seconds to restore the controls.

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 laps by driving distance and show speed, altitude, longitudinal acceleration, estimated lateral G and GPS accuracy with checkpoint markers.

Pro Telemetry: when Pro is enabled, the analysis tools can compare other drivers, scrub the lap by track position, inspect time delta and sectors, compare against racing lines and use shortcuts such as your best lap versus the fastest available reference.

Your normal GPS laps are still recorded without Pro. Pro changes the advanced analysis tools, not the basic lap recorder.

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

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.

Android Native GPS app: download /app/LapSector.apk using the button below. The APK opens the same LapSector website and therefore uses the same login, tracks, sessions and server database. Inside the APK, Android FusedLocationProvider supplies location data through a native bridge to the existing LapSector timing code.

Manual APK installation: because the APK is downloaded directly from the LapSector website rather than Google Play, Android may ask you to allow this browser to install unknown apps the first time. You can disable that permission again after installation.

PWA: if you prefer not to install the APK, use the browser Install prompt or Add to Home Screen. The PWA uses browser Geolocation while the Android APK uses the native GPS bridge.

Same server data: both versions connect to the same LapSector account and APIs, so saved tracks, laps, start tests, cars and sessions remain on your account rather than being tied to one phone.

Automatic web 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 web 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.