Compass is one of the four great inventions in China. It always points to one end.

According to the characteristic that the compass can refer to the north and south on the surface of the earth, it is inferred that the earth has a magnetic field, which is called geomagnetic field. The magnetic field of the earth is very similar to that of a bar magnet.

According to the characteristic that the N pole of the small magnetic needle points to the north, it is analyzed that the direction of the geomagnetic field is from south to north, and it is concluded that the N pole of the geomagnetic field is really near the geographical south pole, while the S pole of the geomagnetic field is near the geographical north pole, and the geomagnetic north and south poles are opposite to the geographical north and south poles.

The extended data compass is the result of the long-term practice of working people in ancient China. As one of four great inventions of ancient china, its invention has played an inestimable role in the development of human science, technology and civilization. In ancient China, the compass was first used for rituals, etiquette, military affairs and divination, and to determine the orientation when looking at geomantic omen.

Modern people have made all kinds of electronic compasses. Smartphones generally have this software. Electronic compass, also known as digital compass, is a method to determine the North Pole by using geomagnetic field. When applied to a mobile phone, it is actually an electronic compass. An electronic compass generally consists of a magnetoresistive sensor and a fluxgate.

Although GPS is widely used in navigation, positioning, speed measurement and orientation, its accuracy is greatly reduced or even unusable because its signals are often blocked by terrain and objects. Especially in urban areas with high-rise buildings and forest areas with dense vegetation, the effectiveness of GPS signals is only 60%.

Moreover, at rest, GPS can't give course information. In order to make up for this deficiency, the method of integrated navigation and positioning can be adopted. Electronic compass is designed to meet this demand of users. It can effectively compensate the GPS signal, ensure that the navigation and positioning information 100% is effective, and it can work normally even if the GPS signal is out of lock, so as to achieve "missing the star without losing direction".

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