Compasses

A compass, (or mariner compass) is a navigational instrument for finding directions on the Earth. It consists of a magnetized pointer free to align itself accurately with Earth's magnetic field, which is of great assistance in navigation. more...

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The face of the compass generally highlights the cardinal points of north, south, east and west. A compass can be used (to calculate heading) in conjunction with a marine chronometer (to calculate longitude) and a sextant (to calculate latitude) to provide a somewhat accurate navigation capability. This device greatly improved maritime trade by making travel safer and more efficient.

An early form of the compass was invented in China around 1044. The familiar mariner's compass was invented in Europe around 1190, from whence later originated the liquid magnetic compass. Fundamentally, the classic compass is any magnetically sensitive device able to indicate the direction of the magnetic north of a planet's magnetosphere. Often compasses are built as a stand-alone sealed instrument with a magnetized bar or needle turning freely upon a pivot, or floating in a fluid, thus able to point in a northerly and southerly direction.

Many enhancements have been developed. A compass dial is a small pocket compass with a sundial. A variation compass is a specific instrument of a delicate type of construction. It is used by observing variations of the needle. An orienteering compass consists of a ruggedized needle compass permanently attached to a transparent baseplate containing tools to assist the user in working with maps in a field setting (as opposed to in an office at a desk).

A recent development is the electronic compass, which detects the magnetic directions without requiring moving parts. This device frequently appears as an optional subsystem built into Global Positioning Satellite Receivers (GPSRs).

There are other, more accurate, devices for determining north (known in such cases as true north, as opposed to magnetic north), which do not depend on the earth's magnetic field for operation. A gyrocompass or astrocompass can be used to find true north, while being unaffected by stray magnetic fields, nearby electrical power circuits or nearby large masses of ferrous metals.

Impact in the Mediterranean

Although critics like Kreutz feels that it was later in 1410 that anyone really started steering by compass.

Mining

The use of a compass as a direction finder underground was pioneered by the Tuscan mining town Massa where floating magnetic needles were employed for determining tunneling and defining the claims of the various mining companies as early as the 13th century. In the second half of the 15th century, the compass belonged to the standard equipment of Tyrolian miners, and shortly afterwards a first detailed treatise dealing with the underground use of compasses was published by the German miner Rülein von Calw (1463-1525).

Read more at Wikipedia.org