What Is a Compass Used For?

A compass is a navigational tool that marks direction according to the earth's rotation cycle or its magnetic field. Compasses can be used for plotting and tracking journeys of predetermined direction on land or at sea.

Primitive compasses were first used by the Chinese circa the 4th century B.C. as a way of navigating their path and harmonizing their environment. The creation of these instruments was based on the ancient practice of feng shui with the purpose of coordinating free-flowing environmental energy. The Chinese used a board with a spoon. The ladle of the spoon was the needle, or pointer, and it always pointed south.

A modern-day compass uses a magnetized needle that serves as a pointer for determining direction. The needle of a modern-day compass always points north to align itself with the magnetic north of the Earth.

The compass card comes labeled with the cardinal points (north, south, east, and west), which clearly provide the navigational markings. The magnetized pointer finds these points in its pull toward the Earth's magnetic field. In the Northern Hemisphere, a compass needle attracts the magnetic south pole, and vice-versa, because unlike poles attract.

However, Earth's magnetic field is relatively weak compared to gravity and friction. For the needle to respond to the earth's magnetism, these more substantial forces must have a lower threshold: the needle must be lightweight and mounted with minimum frictional resistance. To establish an intended direction or the cardinal points, the magnetic force should have less gravity and friction to overcome.

Common problems for compasses include a crazed or cracked dome, where this threshold suffers damage from increased pressure. The damage can result from a fall or excessive sun exposure, which usually leads to a bubble and indicates more gravitational and frictional influence; thus, needle's sensitivity to the magnetic field lessens and the compass becomes inaccurate.