Leonardo da Vinci’s distance-measuring device is an odometer.
Leonardo designed a wheel-based odometer in which a cart wheel turned a series of gears as the cart moved. After a set distance, the mechanism released a pebble into a container. Counting the pebbles provided an estimate of the total distance traveled.
The design is a mechanical ancestor of modern odometers, which record distance traveled by a vehicle. Leonardo’s version did not display a number on a dashboard; it used a physical counting method that connected wheel rotation to measured travel.
Odometers existed in ancient engineering before Leonardo, so he was not the first person to conceive distance measurement by wheel. His drawing is nevertheless a clear Renaissance example of gearing applied to surveying and transport. It is also distinct from a speedometer, which measures speed rather than accumulated distance.