Leonardo da Vinci designed an odometer to record the distance travelled by a cart.
His cart-based mechanism used a wheel whose rotations were transmitted through gears to a counting device. As the wheel turned, the mechanism could register the distance covered. This made the instrument useful for surveying, mapping, and measuring roads or routes.
An odometer measures distance, not speed. That distinction matters because Leonardo also studied motion, timing, and mechanical measurement in other designs. His odometer was a refinement of a much older idea: ancient engineers had already used wheel-based distance counters, but Leonardo’s drawing shows an elaborate Renaissance gear system.
The design should not be confused with a modern vehicle odometer, which is compact and electronically calibrated. Leonardo’s proposal was mechanical and depended on the known circumference of its measuring wheel.