How does the compass distinguish between true and false?

The invention of compass with physical direction indication consists of trilogy: Sina, magnetic needle and compass. All belong to China's invention. [ 1]? Compass is one of the four great inventions in ancient China, and its invention has played an inestimable role in the development of human science and 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: "The shipowner (helmsman) knows geography, watches the stars at night, watches the sun by day, and watches the compass in the dark." [2]? Compass is an all-weather navigation tool applied to navigation, which makes up for the shortcomings of astronomical navigation and geographical navigation and opens a new era in the history of navigation. At the same time, navigation activities further promoted the development of compass. [