A minute of arc, also known as arcminute is an unit of angle equal to 1⁄60 of a degree, or 1⁄21600 of a circle . It is used in fields that involve very small angles such as optometry, navigation and marksmanship.
The milliradian ('mil') was first used in the 19th Century by Charles-Marc Dapples, who was a professor at the University of Lausanne. At the beginning of World War I, France started experimenting with using milliradians on artillery sights instead of decigrades (circle/4000). They were used by France alongside decigrades during World War I. The United States, who copied many French artillery practices, also adopted mils.
Along with the degree,arc minutes and seconds are the most commonly used angular measurement units
- An arc minute can be divided into 60 arc seconds
- There are 60 arc minutes in a degree and 21,600 arc minutes in a circle.