Compass is called compass, which was created in the era of Xuanyuan Huangdi, and later passed down by the sages of past dynasties. It was revised and perfected by observing the ups and downs of mountains, rivers and plains on the earth according to the principles of Yijing and Heluo. It is used to determine the direction and survey the terrain. Most geologists and sailors call it "compass" or "Luo Geng", but seldom call it "compass".
There are many kinds of compasses, such as ternary disk, three-in-one disk, ternary three-in-one dual-purpose disk, easy disk, mysterious disk, and unique disks of users in various schools. However, no matter what kind of compass it is, there must be a layer in the middle that is in the direction of the twenty-four mountains. From the north, they are Renzigui, Ugly Genyin, Jiamaoyi, Chen Xunsi, Bingwuding, Shen, Geng Youxin and Xu Ganhai. * * * Twenty-four directions.