The compass is a magnetometer (used for measuring the Earth’s magnetic field), for navigation and orientation that shows direction. The structure of a compass consists of the compass rose, which displays the four main directions on it: East (E), South (S), West (W) and North (N). The angle increases in the clockwise position. North corresponds to 0°, so east is 90°, south is 180° and west is 270°.
The history of the compass started more than 2000 years ago during the Han dynasty (202 BC – 220 AD) in China. The first compasses were made of lodestone, a naturally magnetized stone of iron. It was called the “South Pointing Fish” and was used for land navigation by the mid-11th century during the Song dynasty (960–1279 AD). Later compasses were made of iron needles, magnetized by striking them with a lodestone.
The first usage of a compass in Western Europe was around 1190 and in the Islamic world by 1232. Dry compasses begin appearing in Medieval Europe and the Medieval Islamic world. They were replaced in the early 20th century by the liquid-filled magnetic compass.
Why does the military use a lensatic compass?
The lensatic compass is the current military compass used. Compared to other kinds, a lensatic compass allows bearings to be read while sighting the objects at the same time without changing eye position. It also has a sighting wire, which helps in determining the azimuth (the horizontal angle or direction of a compass bearing) more accurately.