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About this tool
Record speed-normalized road jolts from your device's accelerometer and GPS.
Road Roughness Logger records road jolts from a phone's accelerometer alongside a live GPS track, timestamping every reading so bumps can be matched to a place and a speed. It flags a jolt whenever the total acceleration including gravity exceeds 12 m/s² — roughly 2 m/s² above the ~9.81 m/s² a stationary device reads — and logs each GPS fix with latitude and longitude to six decimals, speed converted to km/h, and the reported accuracy in metres. It is for anyone who wants evidence about a rough stretch of road rather than an impression of one.
Open Road Roughness Logger on AltFTool — it loads instantly in your browser.
Mount the phone so it moves with the vehicle rather than rattling loose, then press Start with permission to allow motion and location.
Drive the route: any device-motion sample whose acceleration including gravity exceeds 12 m/s² is appended as a Jolt row with its magnitude.
Watch Live local readings fill with timestamped GPS fixes — latitude and longitude to six decimals, speed in km/h, accuracy in metres — then press Stop sensor.
Accelerometer events and GPS fixes are appended to the same timestamped log, so a spike can be traced to the point on the route where it occurred.
Rows are only written above 12 m/s² of total acceleration, so you know exactly what counted as a jolt instead of trusting an opaque score.
The GPS watch runs with high accuracy enabled and no cached positions, and every fix carries its own accuracy figure in metres so you can discard weak fixes.
Any device-motion sample whose combined X, Y and Z acceleration including gravity exceeds 12 m/s². Since a phone lying still already reads about 9.81 m/s² from gravity alone, that threshold corresponds to roughly 2 m/s² of genuine vertical disturbance.
The magnitude is the vector length across all three axes, so orientation does not change the trigger, but mounting does change the reading. A phone rattling loose in a cup holder registers its own movement as road roughness — clamp it to the car so it moves with the vehicle.
Because the browser's Geolocation API only reports speed when the device can derive it, typically from consecutive GPS fixes while moving. Stationary starts, indoor use and some desktop browsers return null, and the log records that rather than guessing a value.
No. Consumer phone accelerometers are uncalibrated and sampling rates vary by device and browser, so the output is indicative rather than a certified roughness index such as IRI. Use it to spot and document problem stretches, not to certify pavement condition.