What measuring device did Leonardo da Vinci design as an early odometer?

Leonardo da Vinci designed a wheel odometer to measure distance traveled.

An odometer records how far a vehicle or other moving object travels. Leonardo’s design used a measuring wheel connected to gears. As the wheel turned, the gearing advanced a display or counting mechanism, allowing rotations to be converted into distance.

This idea suited Leonardo’s work on surveying, roads, canals, and military engineering. A known wheel circumference provides a basic unit of distance, while the gears allow repeated rotations to be counted. The design belongs to the same broad family as ancient distance-measuring instruments, but Leonardo’s drawings show an inventive Renaissance mechanical arrangement.

An odometer does not measure speed directly. Speed requires distance divided by time, whereas the odometer records accumulated distance. Modern car odometers use electronic sensors, but the underlying principle—counting wheel rotation—remains closely related to Leonardo’s mechanical concept.