Compass

Navigation

A compass (or mariner's compass) is navigational instrument for finding
directions. It consists of a magnetised pointer free to align itself
accurately with Earth's magnetic field. A compass provides a known reference
direction which is of great assistance in navigation. The cardinal points
are north, south, east and west. A compass can be used in conjunction with a
clock and a sextant to provide a very accurate navigation capability. This
device greatly improved maritime trade by making travel safer and more
efficient.

A compass can be any magnetic device using a needle to indicate the
direction of the magnetic north of a planet's magnetosphere. Any instrument
with a a magnetized bar or needle turning freely upon a pivot and pointing
in a northerly and southerly direction can be considered a compass. 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. A gyrocompass can also be used to
ascertain true North.

History of the navigational compass

Compasses were initially used in mysticism in ancient China. The first known
use of Earth's magnetic field in this way occurred in ancient China as a
spectacle. Arrows were cast similarly to dice. These magnetised arrows
aligned themselves pointing north, impressing the audience.

Curiously, this trick did not seem to get used by the Chinese for naval
navigation. The knowledge of the behavior of long thin magnets and
lodestones had to move to Europe for that to occur. European naval powers
were quick to identify the value of having a compass on board. Celestial
navigation used the constellations and known stars to identify directions.
This was of little or no use in foggy conditions, with overcast sky or
during the day. Early compasses often consisted of a natural lodestone which
was placed on a float in a protected container of water.

Construction of a simple compass

A magnetic rod is required. This can be created by aligned an iron or steel
rod with Earth's magnetic field and then tempering or striking it. However,
this method produces only a weak magnet so other methods are preferred. This
magnetised rod (or magnetic needle) is then placed on a low friction surface
to allow it to freely pivot to align itself with the magnetic field. It
should be labeled and generally has a pointer to North.

Modern navigational compasses

Modern navigational compasses hold a magnetized needle inside a fluid-filled
capsule; the fluid causes the needle to stop quickly rather than oscillate
back and forth around magnetic north. Other features common on modern
handheld compasses are a baseplate with rulings for measuring distances on
maps, a rotating bezel for measuring bearings of distant objects, and a
sighting mirror that lets the user see both the compass needle and a distant
object at the same time. Many modern navigational compasses also include an
adjustment for magnetic declination, the offset between magnetic north and
true north, which varies from place to place on the Earth's surface.

Mariner's compasses can have two or more magnetic needles permanently
attached to a compass card. These move freely on a pivot. A mariner reads
this for a reference box mark that representd the ship's headings. The card
is divided into thirty-two points (known as rhumbs). The glass-covered box
(or bowl) contains a suspended gimbal within a binnacle. Thihs preserves the
horizontal position.

Points of the compass

The thirty-two points of division of the mariner's compass card. The
corresponding dividing points of the horizon circle with four markings of
the directions [i.e., east, west, north, and south]. These are called
cardinal points. Tthe rest are named from their respective directions. A
compass card is a circular card that is attach to the needles of a compass.
On the compass card are marked the thirty-two points.

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Mathematics

In math and drafting, device known as a compass (or pair of compasses) is
used by mathematicians and craftsmen in geometry to draw or inscribe a
circle or arc. Simply, this type of compass is used as a drafting instrument
used for drawing circles.

Construction

In carpentry, architecture, and shipbuilding, a compass is a curve (or bent)
circular form. A compass plane is a craftsman plane, which has a convex
direction length on the underside, for smoothing the concave faces of curved
woodwork. A Compass saw (or fret saw or keyhole saw) is a narrow blade a saw
that cuts a curve. A compass timber is a curved (or crooked) timber. A
compass window is a circular bay window (or oriel window).

A Surveyor's compass (or circumferentor) is an measuring instrument used in
surveying horizontal angles.

Botany

In Botany, a compass plant {or compass flower; also called rosinweed} is an
American prairies plant and is similar to a little sunflower. It's
scientific name is Silphium laciniatum. The compass plant has it's lower and
root leaves vertical. Compass plants tend to align their edges north and south.

Electronics

COMPASS is an acronym for COMPrehensive ASSembler. COMPASS is a assembly
language on Control Data Corporation computers.

Law

In Law, a compass is to purpose (or intend) something. It is an indivudaul
that is imagining something or to plot a plan. Compassing signifies a
purpose (or design) of the mind (or will), and not carrying such design to effect.

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