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Last updated on April 23, 2014 at 12:54 EDT

Compass

The compass is a tool that helps the user navigate using the Earth’s magnetic poles by using a magnetized pointer that reacts to magnetic fields. Since a compass can be used to calculate a heading it quickly improved the safety and efficiency of travel, especially ocean travel. It has only recently been replaced by Global Positioning Systems. It works by indicating the direction of the magnetic north of a planet’s magnetosphere. Generally the face of a compass highlights the north, south, east, and west directions with a magnetized bar or needle that turns freely upon a pivot. The Chinese invented the compass around 247 B.C. and the dry compass was created in medieval Europe around 1300 AD.

Prior to the compass navigation at sea was done through landmarks and the positioning of celestial bodies. The compass, however, allowed mariners to safely navigate away from land and contributed to the Age of Discovery. Although there is some disagreement as to when the compass was invented there are some references to prove its age. Wang Xu wrote in the 4th century BC about a lodestone that attracts iron. In 1088, Shen Kuo wrote about the rubbing of a needle with a lodestone in order to magnetize it. Zhu Yu wrote of the first actual use of a magnetized needle for navigational purposes in 1119.

These first compasses were needles floating in water; however, the Chinese did make some use of the dry compass. There is only one mention of a Chinese dry-mounted needle and no evidence that Chinese mariners ever used them. There is some questioning on what happened after the compass first appeared in china. Some believe it made its way towards Europe on the Silk Road, others believe there was a direct transfer to Europe, while others believe Europe created the compass independent of China.

The compass is not reference in the Arab world until about 1282. It was used in 1187 in the English Channel and in 1269 a floating compass is described for astronomical purposes as well as a dry compass for seafaring. The compass quickly allowed for travel during the winter months were as before it was discouraged due to the skies being undependable.

In the 14th century a magnetic compass that also had a universal sundial was invented by Ibn al-Shatir. During that same era Arab navigators introduced the 32-point. In 1300 the dry mariner’s compass was invented in Europe. It consisted of a freely pivoting needle on a pin enclosed in a box with a glass cover and a wind rose. Compasses were later fitted into a gimbal mounting to reduce grounding of the needle. Flavio Gioja is credited with perfecting the sailors’ compass by suspending its needle over a compass card.

The bearing compass allows the taking of the bearings of objects by aligning them with the lubber line of the bearing compass. The surveyor’s compass is designed to help with map making by measuring the heading of landmarks and measure horizontal angles. Both types of compasses were in common use by the early 18th century. The bearing compass eventually was reduced in size to be carried in one hand. A patent for the hand compass was granted in 1885. Gunnar Tillander invented a new bearing compass in 1928. His design also had a protractor built in and by 1932 the Silva Company was formed and selling their Silva compass.

Liquid compasses were adapted for aircraft in 1909 by F.O. Creagh-Osborne whose compass used a mixture of alcohol and distilled water to damp the compass card. He soon adopted his design to a pocket model for use by infantry. Tuomas Vohlnen created a lightweight celluloid compass which was wrist mounted. The design led directly to the lightweight liquid field compass of today. Solid state compasses can be found in clocks, mobile phones, and other electronic devices and are designed to provide data for a microprocessor. GPS receivers can attain an accuracy of 0.5°.

The compass works by pointing to “magnetic north” however the distance between magnetic north and true north will increase the farther one is from the prime meridian of the Earth’s magnetic field. The compass does really well at the equator where it far from the “magnetic north”, but the closer the compass moves to one of the magnetic poles the more sensitive it becomes to crossing its magnetic field lines. The needle will start to point up or down when getting closer to the poles which can cause cheap compasses with bad bearings to get stuck. The compass can also have errors when accelerate or decelerated in an airplane or automobile.

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Compass