Before the compass was invented, a captain's only guide to his position was his knowledge of winds, tides, landmarks, and the sun and stars. In open, unfamiliar waters he could only guess which way he was going. The Chinese are thought to have invented the compass as far back as the first century A.D. The original device consisted of a floating piece of magnetized iron in a bowl of water. The Arabs used the compass as early as the eighth century. It reached Europe in the 12th century.

The ordinary magnetic compass was satisfactory for most kinds of navigation until magnetic deviation became a problem with the development of steel ships in the 19th century. This problem was finally overcome with the invention of the gyrocompass in 1906. Aerial navigation requires several different types of compasses that must be constantly checked one against the other. Special compasses have been developed for work near the North and South poles.