What are the laws of tilt error, displacement and projection difference respectively?

The greater the inclination angle, the greater the error. The tilt error is directly proportional to the square of the distance between the image point and the isocenter, and inversely proportional to the focal length of the camera, that is, the closer the image point is to the edge of the photo, the greater the tilt error. The smaller the focal length. Projection difference: image point displacement caused by topographic relief.

When an oblique photo and a horizontal photo with the same main distance of the same camera station overlap along the isochromatic line, the image point of the ground point on the oblique photo is linearly displaced from the image point on the corresponding horizontal photo. Geometrically speaking, the isochromatic line can be regarded as the intersection of an oblique photo and a horizontal photo, which have the same principal distance from the same camera station.