What was the ancient sundial used for?

A sundial is a pointer with a fixed length, which tells time through light and shadow. The projected sundial will change its length and direction, so it can be timed by observing the direction of projection. The equatorial sundial indicates the time by the uniform change of the projection direction of the pointer, so it is easier to read the sundial of time. From the last article, we know that the change of the length of the sundial includes the annual change, so in some sundials. A sundial After pre-calculation, a complex line can be drawn on the surface of the sundial According to the length of the sundial, the time and solar terms can be read at the same time.