The distance-measuring device Leonardo da Vinci designed was an odometer.
Leonardo’s odometer used the rotation of a wheel to calculate how far a cart had traveled. A wheel of known circumference turned as the cart moved, while a counting mechanism recorded the revolutions. Multiplying the number of turns by the wheel’s circumference gave an estimate of the distance covered.
His design belongs to a long history of mechanical distance measurement. Ancient Roman surveyors used related wheel-based ideas, and later devices adapted the principle for roads, surveying, and vehicles. Leonardo’s contribution was to document a practical, mechanically organized version in his notebooks.
An odometer measures distance, while a speedometer measures speed. A pedometer counts a person’s steps, and an anemometer measures wind speed, so those instruments are not equivalent answers. Leonardo’s device was a conceptual ancestor of mechanical distance counters rather than a modern electronic car instrument.