Leonardo da Vinci designed an odometer with a wheel and a counting mechanism to record distance.
An odometer measures the distance traveled by a vehicle or moving device. Leonardo’s design used a wheel that turned as it moved across the ground, transferring motion through gears to a counting system. The mechanism could record distance in a form useful to surveyors, engineers, or military planners.
Leonardo’s notebooks contain several studies of gears, wheels, and measuring instruments. His odometer belongs to that wider program of making motion measurable and repeatable. It should not be confused with his self-propelled cart, which was intended to move on its own.
Modern vehicle odometers still use the same basic principle: movement of the wheels is converted into a numerical distance. Electronic systems now usually replace the mechanical gear trains found in early designs.