Leonardo da Vinci designed an odometer, a device for measuring how far a cart traveled.
His design used a wheel whose rotation was connected to a counting mechanism. As the cart moved, the wheel turned and triggered a sequence of movements that could record distance. The concept is mechanical rather than electronic, but it follows the same basic principle used by many later odometers.
Leonardo's cart odometer is commonly associated with his studies of surveying and military engineering. Accurate distance measurements were useful for mapping, planning roads, and estimating positions in the field. The device was a design recorded in his notebooks, not a mass-produced Renaissance instrument.
An odometer records distance, whereas a speedometer records speed at a particular moment. Leonardo's design should also be distinguished from a pedometer, which is intended to count a person's steps rather than the revolutions of a vehicle wheel.