Compass

Compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with magnetic north. Other methods may be used, including gyroscopes, magnetometers, and GPS receivers.

Compasses often show angles in degrees: north corresponds to 0°, and the angles increase clockwise, so east is 90°, south is 180°, and west is 270°. These numbers allow the compass to show azimuths or bearings which are commonly stated in degrees. If local variation between magnetic north and true north is known, then direction of magnetic north also gives direction of true north.

The locations of the Earth's magnetic poles slowly change with time, which is referred to as geomagnetic secular variation. The effect of this means a map with the latest declination information should be used. Some magnetic compasses include means to manually compensate for the magnetic declination, so that the compass shows true directions.

Some features of Compass are listed as:-

1. The base plate mounting of the compass, with a ruler for measuring scale.
2. The compass housing contains the magnetic needle and has the points of the compass printed on a circular, rotating bezel.
3. The compass needle floats on liquid so it can rotate freely, the blue end should always point to magnetic north.
4. Orienting lines fixed within the compass housing and designed to be aligned with the vertical grid lines on a map. Half the lines are coloured blue to indicate north.
5. Orienting arrow fixed within the compass housing, aligned to north on the housing.
6. The index line fixed within the outer edge of the compass housing as an extension of the direction of travel arrow. It marks the bearing you set by rotating the compass housing.
7. Magnifier for detailed map reading.
8. The direction of travel arrow shows the direction that you want to travel along or the bearing you are taking. It is fixed parallel to the sides of the base plate and aligned with the fixed index line on the edge of the compass housing (number 6).
9. Compass scale displayed along the edge of the base plate so you can measure distances on maps.
10. Luminous strip to assist navigation at night.

In a nutshell, compass is one of the most important instruments for navigation. Magnetic compasses are the most well known type of compass. They have become so popular that the term “compass” almost always refers a magnetic compass.