Leonardo da Vinci designed an odometer to record travel distance.
His odometer concept used a wheel and a gear mechanism. As the wheel moved along the ground, the mechanism counted rotations and transferred them to a display or container. In one version, a series of falling objects indicated the distance traveled by accumulating in a receptacle.
The basic principle is the same as that of later mechanical odometers: distance can be estimated by counting the rotations of a wheel with a known circumference. Leonardo applied this idea to surveying and military engineering, where accurate measurements of roads and terrain were valuable.
Leonardo was not the first person to imagine measuring distance mechanically. Ancient engineers, including Vitruvius’s tradition, described related devices. His importance lies in the clarity and sophistication of his surviving designs, not in inventing the general idea of distance measurement from nothing.