Is the compass of modern daily life useful?

Compasses are often used in navigation, geodesy, travel and military affairs. There are three inventions of compass that indicate the direction physically, namely Sina, compass and magnetic needle, all of which belong to China's invention.

According to the polarity of the earth's magnetic field, the north-south direction indicated by the geomagnetic compass is different from the real north-south direction, and there is a magnetic declination;

Electronic compass adopts the magnetic resistance (MR) technology of magnetic field sensor, which can correct the magnetic declination well and has been widely used in GPS positioning equipment.

Compass, also called Sina, is mainly composed of magnetic needles installed on the shaft. Under the action of natural geomagnetic field, the magnetic needle can rotate freely and keep in the tangent direction of magnetic meridian, and the north pole of the magnetic needle points to the geographical north pole, so the direction can be distinguished by this property.