Why do aerial photography need vertical shooting?

Test and analysis: the working principle of the camera is the real image principle that the convex lens shrinks up and down when the object distance is more than twice the focal length. Because the object distance is much larger than twice the focal length when the plane takes pictures from high air to ground, according to the imaging law of convex lens, when the object distance is larger than twice the focal length, the close-up image of the object becomes smaller, indicating that the imaging distance at this time should be slightly larger than the focal length, that is, slightly larger than 50 mm