Tianchi, also known as "the bottom of the sea", is a compass. The Tianchi of the compass consists of thimble, magnetic needle, submerged wire, cylindrical outer box and glass cover, which are fixed in the center of the inner disk.
There is a sharp thimble in the center of the bottom surface of the round box, and a concave hole in the center of the bottom surface of the magnetic needle, and the magnetic needle is placed on the thimble. The arrow of the compass points south at one end and north at the other.
There is a red line at the bottom of Tianchi Lake, called "submarine line", and there are two red dots on both sides of the northern end. When in use, it is necessary to make the northern end of the magnetic needle coincide with the seabed line.
The inner disk is a rotatable disk next to the outside of the compass. Many concentric circles are printed on the inner disk, and one circle is called a layer. Each layer is divided into different equal parts, some layers have more grids, some layers have less grids, the least one is only divided into 8 grids, and the layer with the most grids has 384 grids. Different characters are printed on each grid.
The outer disk is square, which is the tray of the inner disk. There is a small hole at the midpoint of the outer side of the four sides, and the red line penetrates into the ten meridians of Tianxin, which is used to read the contents of the inner disk. The ten directions of Tianxin are required to be perpendicular to each other, and the new compass you just bought must be calibrated before use.
There are many kinds of compasses, some with many layers and some with few layers. 52 floors at most and 5 floors at least. All feng shui schools have incorporated their main contents into the compass, making our compass an encyclopedia of ancient technology in China.