Arrancada

Arrancada times how long your car takes to reach a target speed, and it does it properly. One run, the one everybody quotes: 0-100 km/h, or 0-60 mph if you prefer imperial. Splits along the way. WHY THE NUMBER IS ACTUALLY RIGHT A GPS receiver reports about once a second. Your car can already be moving well before the first sample shows it, and a timer that treats that sample as the start flatters every run by up to a full second -- enough to turn a 7.6-second car into a 6.8-second one. Arrancada fits a curve through the start of the pull and extrapolates back to the instant speed would have been zero. A straight line is the wrong shape for that, because acceleration falls away as the car gains speed, so it uses a least-squares quadratic. On a run sampled at 1 Hz, a linear fit lands 60 ms out; the quadratic lands 6 ms out. The estimate is then clamped between the last stationary reading and the first moving one, so a bad fit can never do worse than the naive answer. The finish is interpolated between the two samples that bracket your target speed, because the target almost never falls exactly on a sample. BUILT TO NOT LIE TO YOU - A dead band between "stopped" and "launched", so receiver noise at rest cannot start a run - A 1.6g plausibility ceiling, because stationary to 80 km/h between two samples is bad data, not a quick car - The run aborts if the fix is lost mid-way -- a time you cannot trust is worse than no time - Reads the receiver's own Doppler speed rather than the smoothed, sensor-blended fused location, because smoothing is lag and lag is exactly the error being removed FULL-SCREEN COCKPIT A dark, high-contrast readout designed to be legible at a glance in daylight. Tap to switch to the built-in simulator, long-press to switch between km/h and mph. KEEPS YOUR RUNS Your last 50 completed runs are kept on the device, with a separate best time for 0-100 km/h and 0-60 mph -- 60 mph is 96.6 km/h, so the two are not the same run and are not compared. Nothing is uploaded. Arrancada has no server, no account, no analytics and no ads -- there is no networking code in the app at all. NEEDS PRECISE LOCATION Speed comes from the GNSS receiver, which is the only way to measure acceleration accurately. Location is read only while the app is open, never in the background, and never leaves your phone. Decline the permission and the app still runs in simulator mode. A WORD ON SAFETY Measuring acceleration means accelerating hard. Use Arrancada only where it is legal and safe -- a closed course or a private road. Never interact with your phone while driving.