This invention revolutionized navigation and exploration by providing a reliable way to determine direction. The compass was invented in China during the 11th century and is believed to have been used by the Chinese for navigation since the 4th century. It consists of a magnetized needle that is balanced on a pivot
From Wikipedia
The compass is a magnetometer used for navigation and orientation that shows direction in regard to the geographic cardinal points. 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°, east is 90°, south is 180° and west is 270°.