How to read the east longitude and north latitude in the picture?
The earth is a big magnet, and its geomagnetic south pole is near the geographical north pole, and the geomagnetic north pole is near the geographical south pole. The compass is influenced by the magnetic force in the earth's magnetic field, so it will be guided at one end and pointed to the north at the other end.
Once the compass was invented, it was quickly applied to military affairs, production, daily life, topographic survey and other aspects, especially navigation. The application of compass in navigation has a gradual development process.
The compass was first invented by China, and later it evolved into a compass and was used in navigation. The book Zhou Ping Ke Tan written by Mi Zhu in the Northern Song Dynasty recorded the application of compass in navigation for the first time. "Sailors know geography, but they look at the stars at night and the sun during the day, and their compasses are blurred." Later in the Southern Song Dynasty, Fujian Road Shipping Agency (the government agency in charge of foreign trade at that time) mentioned in Zhao's "Fan Zhi Lu" that "the boat travels, but it is better to watch around the clock with a compass."
Compass is the result of the understanding of the magnetism of objects by the working people of ancient Han nationality in long-term practice. 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. 1 1 At the end of the century or at the beginning of the 2nd century, China ships began to use compasses for navigation. Zhou Ping can talk in the Northern Song Dynasty: "Sailors know geography, watch the stars at night, watch the sun by day, and watch the compass in the dark."