Leonardo da Vinci designed an odometer that measured distance by counting wheel rotations.
An odometer records how far a vehicle or cart travels. Leonardo’s design used a wheel whose rotation drove a counting mechanism, allowing a measured distance to be tracked as the wheel moved over the ground. His version was intended for surveying and mapping rather than for a modern automobile dashboard.
The concept depends on a simple relationship: if the wheel’s circumference is known, each complete turn represents a fixed distance. Gears can convert repeated wheel rotations into visible increments on a display or a set of numbered indicators.
Leonardo did not invent the general idea of measuring travel with a wheel; ancient devices with similar purposes existed. His importance is that he carefully developed a practical Renaissance mechanism and documented it among his engineering studies. An odometer differs from a compass, which indicates direction rather than distance.