lap/line Get it

GPS lap timing and telemetry for karting

lap/line

Find where the time is, corner by corner. Lap timing and telemetry for karting, rental or your own, from the phone you already have. Place the start line once, then just drive.

Get the app See what it measures

v0.1.1 · App Store and Google Play coming soon

    Sector 1 · What it is

    Real numbers. No guesses.

    Your GPS gives position, speed and heading, and a receiver with motion sensors adds g-forces. lap/line turns that into laps, deltas and corners you can act on. When the source is too coarse for a figure, the screen tells you instead of making one up.

    Measured

    • Position and lap distanceEvery fix projected on the track
    • SpeedReceiver Doppler, not differentiated positions
    • CourseHeading of the kart
    • Longitudinal gBraking and acceleration
    • Lateral gSpeed times yaw rate
    • DeltaTime against a reference lap, point by point
    • IMUAccelerometer and gyroscope when the receiver has them

    Not measured

    • VideoNo camera, no overlays
    • Engine RPMNeeds kart sensors
    • Water and EGT temperatureNeeds a dedicated logger
    • ThrottleNot a GPS measure
    • Brake pressureNot a GPS measure
    • Steering angleNot a GPS measure

    What the GPS rate can show

      Sector 1 · The library

      About 2,000 circuits, ready when you arrive.

      Pull into a karting track and it is probably already there: outline, length, corners and how far away it is. Choose it, place the start line once, and ride. A track that is missing takes one lap to scan.

      0karting circuits in the library

      Every dot is a circuit from the bundled file, placed here to about 10 km; distances are rounded to 5 km. Kinds shown in the app (Indoor, Dirt, Circuit, Short, Lit) are read from OpenStreetMap tags and marked approximate. Tracks © OpenStreetMap contributors, ODbL. Land outlines from Natural Earth, public domain.

      Sector 1 · Where the fixes come from

      Your phone is enough. A receiver is the upgrade.

      Time your laps with the phone's GPS. To see a sharper racing line, braking points and corner speeds, add an affordable receiver. Pick one per session. If the receiver drops out for more than 2 seconds, the phone takes over and your lap is not lost.

      Fix spacing at 60 km/h, drawn to scale

      1 Hz16.7 m
      10 Hz1.67 m
      25 Hz0.67 m

      Phone GPS is enough for lap times, not for racing line, braking points or corner speeds.

      Phone GPS

      1 Hz

      Typical rate. The phone's own GPS, read as raw as the system allows, with no fused smoothing.

      External receivers

      • RaceBox Mini, Mini S, MicroBluetooth LE · 25 Hz · GNSS, accelerometer and gyroscopeWaits for its protocol
      • Qstarz BL-1000GTBluetooth Classic · 10 HzPair first
      • Dual XGPS160Bluetooth Classic · 10 HzPair first
      • Garmin GLO 2Bluetooth Classic · about 7 to 8 HzPair first
      • Any NMEA receiverBluetooth Classic · rate variesPair first

      Receivers are proved on the simulator only so far. Bluetooth LE receivers connect directly; Bluetooth Classic ones depend on what the phone's system allows.

      What works on which phone

      SourceAndroidiPhone
      Phone GPS1 Hz, no extra hardware BuiltReads the raw GPS provider. PlannedWaits for its first iOS build.
      Bluetooth LE receiversRaceBox Mini, Mini S, Micro PlannedWaits for the RaceBox protocol. PlannedAfter it exists on Android.
      Bluetooth Classic receiversQstarz, Dual XGPS160, Garmin GLO 2, NMEA BuiltPaired in Bluetooth settings. Not possibleApple only lets apps use Bluetooth Classic accessories through its MFi program.

      Built means it is in the app and tested in code; the checks on real phones and receivers come first. Planned means decided, not built.

      Automatic fallback

      1. No valid fix for more than 2 s.
      2. Timing continues on phone GPS 1 Hz, shown in yellow.
      3. It switches back when the receiver recovers.

      Sector 1 · On track

      Eyes on the track.

      Big numbers in landscape and nothing to tap. Place the start line once and the session times itself, lap after lap. Scroll to run a session.

      1. Start lightsFive lights, one every 600 ms, out together, as soon as your GPS has a fix. Then drive: the first crossing starts the clock.
      2. Live delta and barGreen when gaining, yellow when losing, against your session best. Predicted lap beside it.
      3. Mini-sectorsTwelve by default. Purple beats the record, green is session best, yellow is slower, grey is within the noise of the rate.
      4. Focus cornerThe corner with the most time found last session. After you pass it, its time flashes for 3 s against your best pass.
      5. Sun modeWhite ground, black figures, darker timing colours. For a bright day.
      6. Purple record passA track record replays the logo pass in purple.

      Sector 2 · After the session

      Your race engineer, after every session.

      The lap/line engineer tells you where the time is: up to three corners or straights, in order, each with what it is worth in seconds. It draws your track and lights them one by one, like a team radio call.

      lap/line engineerTeam radio

      Sample session on South Garda Karting. Corners and figures are illustrative.

        Every call comes from one measured difference between your three best passes and your typical one. Below 5 Hz it judges exits and time only. No call names throttle, steering or anything a GPS does not measure.

        Sector 2 · Where you lose time

        Know exactly where you lose time.

        Every lap is lined up point by point, so you see where you brake, how much speed you carry and where you exit. Corners and straights add up exactly to the lap's delta. The sample below is a simulated lap on a real circuit outline.

        Lap telemetry

        Drag across the chart or use the left and right arrow keys. Speed is the receiver's Doppler speed; longitudinal g is dv/dt, lateral g is speed times yaw rate. Delta up means losing time. Lap 8 against lap 7.

        Corner by corner

        Timing tower

        • Track record
        • Session best
        • Slower

        Optimal lap from your best corners

        Laps from your last 8 sessions at 5 Hz or more are cut in the middle of the straights. The fastest valid pass of each segment is stitched into one trace. Below 5 Hz it is not built: noise would pick a lucky pass in every segment. Segments in the drawing are an illustration.

        Rolling best

        The fastest stretch one lap long within consecutive valid laps, wherever it starts.

        Progress over a season

        • S1 typical16.62 → 16.12−0.50
        • S2 typical17.84 → 17.31−0.53
        • S3 typical19.58 → 19.12−0.46

        Progress never compares different precisions: the best lap over the period, every sector across all sessions, and corners only from sessions recorded at 10 Hz or more. Sample figures.

        Sector 2 · Yours

        Your tracks. Your karts. Your setups.

        Any track, any kart. Choose a circuit and set its start line, its sectors and its name in one window, or scan a new track by driving or walking one lap. Rental or your own kart, with the setup saved next to every session.

        Scan a track

        Drive at least 3 laps, easy pace with phone GPS. At 40 km/h a 1 Hz fix lands every 11 m.

        Place the start line

        0 sHold still on the line

        Drag the chequered line along the track, or stand on the real line: the last 15 s of still fixes are averaged, with at least 10 fixes, 10 s held and a spread of 5 m or less. You do it once per track.

        Rental karts by number

        A rental kart is its number at its track: #12 at one track is not #12 at another. Session setup shows the kart's history there: sessions, best lap and last day.

        Own karts and setup

        14
        Chassis and engine, with brand and model
          • Tyre pressure front
          • Tyre pressure rear
          • Sprocket
          • Axle sprocket
          • Notes

          Number plates, specs, record and engine time since service. The setup is saved as a snapshot with each session.

          Sector 3 · Your data

          Your logbook, in your hands.

          Every session, lap and GPS point stays with its kart, track and setup, so next week you start from what you learned, not from memory. Edit a track later and every past lap is timed again from the raw GPS.

          Your logbook
          • Sessions
          • Tracks
          • Raw GPS streams
          • Karts and setups
          • Stopwatch
          • Hand notes
          • Spreadsheets
          • Gut feeling
          • Guesswork

          Export

          • CSVEvery session and lap, from Settings, or one session's laps
          • GPX 1.1Every GPS point of a session, with speed and course as extensions

          Import

          • NMEA log, GPX track, CSVSessions from other apps, RaceChrono's CSV among them
          • GPX or KML lineA track path of at least 10 points whose ends are within 50 m

          Sector 3 · The details

          Built like a timing screen.

          Every number rolls, every lap slides in, every record gets its moment, the way a race timing screen does. With the system's reduce-motion setting on, everything shows its final state.

          Figures roll

          Digits roll up in 120 ms when a value changes. Never on Live.

          Rows slide and sweep

          A new lap slides in at the 12 degree slash angle in 200 ms. A best or record sweeps across its row once, purple for a record.

          The logo pass

          lap/line

          A red line crosses at constant speed, uncovers the wordmark and the slash snaps from white to red. About 1.1 s at launch and when onboarding ends.

          Chequered strip

          End session

          When you end a session a chequered strip crosses the screen in 320 ms.

          Finish line

          Get it.

          Here is where it stands today, with nothing rounded up.

          App StoreComing soonGoogle PlayComing soon
          • Version0.1.1

            The version of the app today.

          • AndroidBuilt

            Phone GPS and Bluetooth Classic receivers. The APK below goes live with a published release.

          • iPhonePlanned

            Phone GPS first. Bluetooth Classic receivers are not possible on iOS; Bluetooth LE ones follow.

          • StoresComing soon

            The App Store and Google Play buttons switch on when their listings exist.

          Outside the stores

          APK not published yet

          Pure telemetry from a GPS receiver and its sensors. Metric units by default.