Leonardo da Vinci’s distance-measuring cart is commonly identified as an odometer.
His design used a cart whose wheel turned a series of gears. After a set number of wheel rotations, a mechanism released a small object, such as a pebble, into a container. Counting the objects would indicate how far the cart had traveled. The concept transformed repeated wheel movement into a practical distance measurement.
Leonardo drew the device in the Codex Atlanticus while studying machines and transport. It was not a modern electronic instrument and was not intended to display speed. An odometer measures distance, whereas a speedometer measures rate of travel. This distinction is a common source of confusion when discussing early measuring devices.
The invention also illustrates Leonardo’s interest in gear trains, counting mechanisms, and military engineering. Similar wheel-based distance measurers were later used for surveying, road measurement, and mapping.