There are many types of sundials, and according to different classification criteria, sundials can be divided into different types. According to the way of use, sundials can be divided into equatorial sundials, horizontal sundials, vertical sundials and projection sundials. In addition, according to the material and manufacturing process, sundials can be divided into copper sundials, iron sundials, stone sundials, wooden sundials and brick sundials. Each of these different types of sundials has its own characteristics and scope of application.
Among the various types of sundials, the equatorial sundial is one of the oldest and most commonly used. It works by projecting the projection of the sun onto a flat surface and calculating the local solar time by measuring the angle between the sun's projection and the local direction due north. Equatorial sundials are relatively simple to make, making them suitable for general use.
Horizontal sundials project the sun's projection onto a straight rod perpendicular to the ground, and measure the length and time of the shadow of the rod to calculate the local solar time. Horizontal sundials are relatively simple to make, but they need to be used with special care because they need to keep the angle between the straight rod and the ground.
Vertical sundials project the sun's projection onto a straight rod that is horizontal with the ground, and the local solar time is calculated by measuring the length and time of the shadow of the rod. Vertical sundials are relatively simple to make, but they need to be kept at a level angle between the straight rod and the ground, so special care is also required when using them.
In addition to the above common types of sundials, there is also a special type of projection sundial. It works by projecting the sun's rays onto a plane through a hole, and by measuring the position and time of the spot, the local solar time is calculated. Projection sundials are more complex to make, but they are more accurate, so they are suitable for use in situations that require high-precision timekeeping.