Compass : The Sailor's 'Google' !

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Just as the Internet user has Google nowadays ('let's GOOGLE it!'), today's sailors have the RADARs and chartplotters !

But in the older days, the sailors had a compass and a sextant for guiding them through endless oceans.


Infact, it would not be surprising to know that even today, many die-hard sailors still use these wholly or in some manner atleast to guide them to thier port-of-call.

...imagine...in days of GPS also!

BUT WHAT IS A COMPASS ?

Simply put, its an instrument that is used for finding directions on the Earth.

The main component of a magnetic compass is a (like you guessed...) a magnetized pointer free to align itself accurately to the earth's magnetic field.


The 'face' of a compass usually highlights the 4 main directions - North, South, East and West which are also known as the 'Cardinal Points'.

In maritime navigation, a compass is surely required with other instruments to calculate key directional parameters viz., with a sextant to calculate latitude; with a marine chronometer to calculate longitude.

HISTORY OF THE COMPASS

No one is sure about when or who made the first compass...but based on findings, magnetism and reference to the earth's magnetic fields has been found in Chinese literature.

'Pre-compass' days, sailors used to calculate position and direction at sea by the sighting of landmarks, supplemented with the observation of the position of celestial bodies.

Ancient mariners usually kept within easy sight of land. The invention of the compass enabled the determination of heading when the sky was overcast or foggy.

And, when the sun or other known celestial bodies could be observed, it enabled the calculation of latitude. This enabled mariners to navigate safely away from land, contributing to the 'Age of Discovery'.

POINTS OF A COMPASS

Since 1100 A.D., the compass bearings have been split into 16 directions.


1) North
2) North North East
3) North East
4) East North East

5) East
6) East South East
7) South East
8) South South East

9) South
10) South South West
11) South West
12) West South West

13) West
14) West North West
15) North West
16) North North West

GYROCOMPASS

A gyrocompass is similar to a gyroscope. It is a compass that finds 'true north' by using an (electrically powered) fast-spinning wheel and friction forces in order to exploit the rotation of the Earth. Gyrocompasses are widely used on ships. They have two main advantages over magnetic compasses.


1) They find true north, i.e., the direction of Earth's rotational axis, as opposed to magnetic north,

2) They are not affected by ferrous metal in a ship's hull. (No compass is affected by nonferrous metal, although a magnetic compass will be affected by non-ferrous wires with current running through them.)

Keep yourself posted...soon you would get to know how to use a compass here...