A compass is used for navigation and can be aligned to magnetic north or true north. The most common type is a magnetic compass, which traces back to 4th century BC China. A gyro compass and astrocompass can find true north. Solid-state and GPS compasses are becoming more common, but traditional compasses are still used in ships and military operations. It is recommended to have a backup form of navigation.
A compass is a device that can determine direction on Earth, usually used for navigation. A compass can be aligned to magnetic north or true north, or occasionally to an arbitrary direction based on the position of celestial bodies. Magnetic north is the direction of the north tip of the Earth’s magnetic field, while true north is the direction in which the Earth rotates.
The most common type of compass is a magnetic compass, which is used to ascertain the direction of magnetic north. A magnetic compass is made by placing a piece of magnetized iron or steel in a low-friction environment so it can move freely. In most compasses, the north end of the piece of metal is marked, most often with red paint, so that all directions can be ascertained.
The use of the magnetic compass can be traced back to 4th century BC China, where a type of lodestone known as a lodestone was used as a tool in a type of divinatory magic known as geomancy. The Chinese mastered the use of magnetic iron for navigation in the early 12th century, and its use quickly spread across Europe and beyond. In the early 13th century, Arabs used the magnetic compass in navigation, and by the early 14th century an Italian had created what would be recognizable to modern eyes as a mariner’s compass.
A gyro compass is a special type of compass developed in the late 19th century, which ascertains true north, rather than the somewhat more fickle magnetic north. A gyrocompass is essentially a very fast spinning wheel or ball that uses the law of conservation of angular momentum and the rotation of the earth’s axis to point towards true north. The gyro compass is commonly used on large vessels and in other situations where a more accurate north reading is required.
An astrocompass is another type of compass that can find true north rather than magnetic north. An astrocompass relies on the position of celestial bodies to find true north, which is useful in a number of situations, particularly at the north and south poles, where magnetic compasses become unreliable and gyrocompasses often stop working. To properly use an astrocompass requires a fair amount of information, including time, date, and longitude and latitude, as well as an astronomical chart such as a nautical almanac. Given this information, a person can stare at a known star and determine the exact direction of true north.
In the digital age, solid-state compasses are also becoming more common. These use a series of electronic magnetic sensors that calculate the precise direction the compass is pointing.
GPS compasses are rapidly replacing many traditional compasses for personal use, although most ships and military operations have a gyro or magnetic compass on hand in case a GPS cannot find enough satellites. GPS compasses use satellites in a geosynchronous orbit around the Earth to discern the bearer’s exact location and the direction they are heading. Because of the ease of use and relative reliability of the GPS compass, many hikers and drivers prefer it. As with all electronics, however, the GPS compass is prone to its own number of problems, and it is recommended that most hikers also have a form of navigation to spare.
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