What is a compass and what is it for?

The compass is one of the greatest inventions of humanity, a device for orientation. Its appearance is comparable to the appearance of gunpowder in warfare. When the compass appeared, the Portuguese and Spaniards ventured into distant voyages which resulted in the Great Geographic Discoveries.

Today there are several compasses – astronomical, magnetic, radio compass, compass oriented to artificial objects, gyrocompass, and satellite compass.

The first in history

The first in history was the magnetic compass. It, like many great things, was invented in China during the Song Dynasty from 960 to 1279 AD. The details of its creation have not been preserved, but the legend was left to descendants. Five thousand years passed after the Chinese emperor Hu An-di waged war with the Mongol khan.

The Mongol army retreated into the desert, pressed by the Chinese. When the Mongols were in their native land, they raised terrible dust that obscured the sun. Knowing the terrain well, the riders fled, but the Chinese completely lost their bearings. – where to go?

When the situation became critical they ran out of water, and ate their supplies – the emperor suddenly remembered that with him was a strange tiny iron man, given to him once by an ancient sage. No matter how you place the little man, he will always point to the south.

The emperor secured the man in his chariot and led his warriors strictly according to the direction of the top-man’s hand. A few days later, those who survived saw their homeland…

The legend took distances from the real terms of the invention of the compass. However, it reflects the essence of the invention – the orientation of the arrow to the north-south.

There is also evidence that Egyptian sailors had magnetic compasses as fish about 800 years ago. To use the compass, they lowered it onto the water, and the “fish” invariably turned its head to the north.

Magnetic compass came to Europe in the XII century with Venetian merchants. It immediately spread with incredible speed, especially among sailors. The compass was perfected by adding an arrow mounted on a sharp needle. Flavio Gioia (Italy) is credited with the transformation of the instrument.

In the sixteenth century, in order to eliminate the effects of rocking, the compass was placed in a gimbal; in the seventeenth century it was equipped with a direction finder.

But no matter what transformations the magnetic compass is subjected to, the principle of its operation – the location of the free magnetic arrow toward the lines of force of the Earth’s magnetic field remains unchanged.

Astronomical compass

It is used to determine the direction of travel by referring to a certain celestial body, most often the Sun. To use the astronomical compass, you need to know the date and the exact time, calculate the azimuth of the celestial body, etc.

The rather complicated determination procedure is compensated for because the astronomical compass always shows precisely the direction, even near the Earth’s magnetic poles or in space. It is indispensable for particularly precise calculations when you can not neglect the variation of the compass, its deviation from true north and south, associated with the mismatch of geographical and magnetic poles.


This type of compass is used to determine the course and azimuth of direction. The creation of the gyrocompass is a credit to the scientist Foucault (France), who gave the idea for the device.

A gyro compass shows the direction of the true pole (the point of rotation of the Earth) and is used in the navigation systems of large ships.

Radio compass

A radio compass, or onboard radio direction finder, is used in air navigation and works by radio signals transmitted from the ground. The radio compass was first used in 1920.

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