Gradian (gon)
The gradian, also known as gon or grad, was established in France following the French Revolution to promote a decimal-based system of angular measurement. In this system, a circle is divided into 400 gradians, resulting in a right angle measuring exactly 100 gradians. The gradian aimed to make calculations easier by matching the decimal metric system. While it did not gain universal acceptance, it remains in use within certain engineering and surveying practices, especially in France and parts of Central Europe. Its straightforward decimal approach is convenient, but degrees and radians are more widely used globally.
Arc Minute (′)
An arc minute (′) represents one-sixtieth of a degree, so a full degree contains 60 arc minutes and a complete circle has 21,600 arc minutes. Its origins trace back to ancient astronomers in Babylon and Greece, who needed finer subdivisions of the degree for celestial observations and mapping. Today, arc minutes are still fundamental in fields such as astronomy, navigation, and land surveying. They are commonly used in geographic coordinate systems—latitude and longitude—where they offer a more precise measurement than whole degrees.