Leonardo da Vinci designed an odometer to measure distance by counting the turns of a wheel.
His odometer concept used a wheel that moved along the ground and a gear mechanism that recorded its rotations. Because the distance travelled by each wheel revolution could be estimated, the mechanism could indicate how far a cart had gone. Leonardo’s version was intended for practical surveying and mapping work.
The idea was not wholly unprecedented: ancient engineers had already developed distance-measuring devices. Leonardo’s contribution was a detailed mechanical design showing how a rotating wheel could drive a counting system. His notebooks frequently connect such mechanisms with military engineering and land measurement.
An odometer measures distance, while a speedometer measures speed. The two instruments are often placed together in modern vehicles, but they answer different questions: how far something has travelled versus how fast it is moving.