As early as ancient times, China used soil rules to determine the orientation. There was Sina in the Warring States Period, Feng Shui compass in the Han Dynasty, and acupoint measuring ruler in the Ming and Qing Dynasties. Tugui uses sunlight to determine the direction, while other tools use the principle of compass to determine the direction. Guo Pu's "Buried Classics" says: "The soil is expensive and its position is measured, and the jade is far and near." Mr. Feng Shui uses these tools alternately.
Measuring tools can be traced back to "table" at the earliest.
According to the shadow of the watch when the sun rises and sets, the direction can be determined.
Tugui was popular in Zhou Dynasty. Earth gauge is an instrument used by ancient philosophers to measure the shadow of the sun and the earth at four o'clock sharp.
The usage of the soil gauge is to erect a wooden pole on the horizontal ground, make the wooden pole perpendicular to the ground with a rope, and then observe the projection of the wooden pole at sunrise and sunset. When the projections on both sides are connected with the intersection of a circle with the wooden pole as the center and the column length as the radius, it is the positive east-west direction. In different seasons, we should master different methods, connect with the stars and determine the correct position.
Now, there is an observatory in Dengfeng County, Henan Province. It is said that Duke Zhou once measured the shadow of the sun here and buried it in peace. There is a stone tablet on the observatory, called a stone watch, which is used to measure the shadow of the sun. The ancients thought this place was in the center of the earth, and called it "the intersection of heaven and earth, the meeting of the four parties, the meeting of wind and rain, and the meeting of yin and yang."