Odometer
An odometer or odograph is an instrument used for measuring the distance traveled by a vehicle, such as a bicycle or car. The device may be electronic, mechanical, or a combination of the two (electromechanical). The noun derives from ancient Greek ὁδόμετρον, hodómetron, from ὁδός, hodós ("path" or "gateway") and μέτρον, métron ("measure"). Early forms of the odometer existed in the ancient Greco-Roman world as well as in ancient China. In countries using Imperial units or US customary units it is sometimes called a mileometer or milometer, the former name especially being prevalent in the United Kingdom and among members of the Commonwealth.
For other uses, see Odometer (disambiguation).Accuracy[edit]
Most odometers work by counting wheel rotations and assume that the distance traveled is the number of wheel rotations times the tire circumference, which is a standard tire diameter times pi (3.141592). If nonstandard or severely worn or underinflated tires are used then this will cause some error in the odometer. The formula is . It is common for odometers to be off by several percent.[18] Odometer errors are typically proportional to speedometer errors.
