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Why Does The Magnetic Compass Installed On The Ship Need To Be Corrected?

Abstract: the article mainly around the magnetic compass points to the principle, the change of ship's magnetic and its effect on the magnetic compass, ship navigation and elaborates the magnetic compass inseparable relationship, on the one hand, this paper introduces the basic principle of magnetic compass, on the other hand shows the magnetic compass in the process of ensure the safety of ship navigation plays important role.

1. Direction principle of magnetic compass.

Our ancestors had discovered the "magnet for iron," or "the guide", more than 2,600 years ago. Later, the invention of "si nan", "si nan" can refer to the north and south, so as to make a compass. This is the great contribution of the Chinese nation to world civilization.

The earth is a large magnet with a magnetic field on its surface, and its two poles are close to the poles of the earth, but they do not coincide, and it moves very slowly. We call the magnetic pole near the North Pole of the earth, near the pole of the earth's South Pole, called the magnetic South Pole.

There is a point in the center of the magnetic needle, when there is no ferromagnetic material around it, the magnetic needle points towards the magnetic North Pole, and the other end points to the magnetic South Pole.

The magnetic compass that we use daily, its core point is the float chamber. In order to get enough of the northern force. Usually in the float chamber, install two or four magnetic rods. The magnetic rod, on the earth's magnetic field, points to "north" (magnetic north) and "south" (magnetic South Pole) at the other end. Fix a dial around the floating chamber and make a baseline on the compass bowl. So we can see where the direction is. But the compass referred to as "north" is not the true north of the earth meridian. The error between magnetic north and true north is called magnetic difference.

2. Changes in ship magnetism and its effect on magnetic compass.

Ships are made of steel. Steel, under the earth's magnetic field, is magnetized and magnetic.

Ships are usually equipped with generators, wires and a large number of electrical equipment. These electrical devices also generate magnetic fields during use. The magnetic field has an effect on the ship itself - the hull is magnetized.

The ship will dock at the same dock for more than a month. Due to the magnetization of the earth's magnetic field, the original magnetism of the ship will also change.

When the ship is subjected to violent vibration, the ship's own magnetic field will also change.

The ship suffered a great storm at sea and the ship was hit by other ships. Or itself in the dock when the collision with the dock and so on. All can change the magnetism of the ship itself.

When a ship is repaired, such as replacing the steel or adding equipment to the ship, especially in the vicinity of the magnetic compass, even the smaller steel parts will have an effect on the ship's magnetism.

When a ship is accidentally caught in a fire shed, even a local fire will have a greater impact on the ship's magnetism. It also affects the magnetic compass.

When a ship loads steel (including magnetite). Because these steel are magnetic. So the magnetism of the hull changes.

It is particularly noteworthy that when the ship is disassembled by a strong magnetic crane, the hull will be seriously magnetized, and the magnetic compass in the ship will be seriously deviated. And the ship's magnetic compass is unstable for a long time! Big change!

The magnetic compass is mounted on the ship. In addition to the earth's magnetic field, it is also affected by the hull's magnetic field. The magnetic sizes of various ships are different. The effect on the magnetic compass installed on the ship is also different. More than 170 ° ~ 180 °, less is 10 ° ~ 20 °. Only after measurement can we know.

3. The navigation of ships requires magnetic compass.

Although modern technology has given the ship precise positioning of the satellite locator. But each ship must install an "old" magnetic compass. It is an indispensable pointing instrument in the navigation of ships. It is also a reliable guarantee for the safe navigation of ships.

The magnetic compass mounted on the ship is not accurate because of its magnetic influence. It is not possible to use it to navigate. Therefore, the magnetic compass must be corrected. Finally, the error on each main course is measured and the deviation table is made. This magnetic compass can be used for navigation to ensure the safety of navigation.