Leonardo da Vinci designed an odometer to record distance by counting wheel rotations.
His cart-like measuring device used a wheel that turned as the machine moved. A linked mechanism transferred each rotation to a counting system, allowing the operator to estimate the distance traveled. The design is often described as an early mechanical odometer and was intended for surveying or mapping.
The key idea is simple: if the wheel’s circumference is known, counting its rotations gives the distance covered. Leonardo’s version used a mechanism that could release a small object at regular intervals, creating a count associated with the wheel’s movement.
An odometer measures distance, not speed. A speedometer measures how quickly something is moving, while an altimeter measures height and a compass indicates direction. Leonardo’s device belongs to his wider interest in accurate measurement, including land surveying, military engineering, and the planning of canals and roads.