What is an anchor point (line)? What is the light law?

The ray method means a measurement method to determine the location of a target point on a current map. First calibrate the orientation of the map and determine the position of the standing point on the map, and then draw a direction line toward the target. After drawing, visually measure the distance from the standing point to the target point one by one, and intercept the distance on the direction line according to the map scale to find the position of the target point on the map. The positioning line is a line used to determine the main location, such as the line that determines the bay or column spacing, depth or span of the building. Light is the soul of photography. Mastering the positioning points, lines and light rules can provide you with an in-depth understanding of light.