Put Guiping in the open air to the north of the table, measure, compare and calibrate the Sunday and anniversary changes of the sun shadow according to the shadow on Guiping, so as to determine the direction, measure the time, find out the anniversary constant, divide the seasons and make a calendar.

Sundial:

The moving shadow of the hand seems to be the pointer of a modern clock, while the surface of the hand is the surface of the clock to show the time. In the morning, shadows are cast near Shi Mao at the western end of the disc. Then, when the length of the shadow remains the same, it moves to the north (below). When the sun reaches the highest position due south (upper meridian), the needle shadow is located due north (lower), indicating the local noon time. In the afternoon, the sun moves west and the shadow leans east, pointing to each hour in turn.

Leak:

Sculpture-Ancient time was measured by clepsydra.

The leaky pot is divided into two parts: the sowing pot and the receiving pot. The seeding kettle is divided into two or four layers, both of which have dripping holes, and finally flow into the receiving kettle. The kettle has an upright arrow engraved with 100 minutes. The arrow gradually rises with the storage of water, showing the number of minutes to show the time.

Leaky pot is also called leaky carving. Leakage refers to the leakage of the pot; Carving means carving an arrow. The arrow is a ruler marked with a time scale. Missing carving is to calculate the time by observing the data displayed on the carved arrow in the pot by using the principle of balanced dripping. The clepsydra is a kind of timer, which shows the time by dripping the water in the clepsydra on the carved arrow. The clepsydra is generally made of copper, and its history can be traced back to Xia and Shang Dynasties.