The orthogonal projection of the perspective centre on a tilted photograph, is called A. Nadir B. Isocenter C. Principal point D. Plumb point

The correct answer is: C. Principal point

The principal point is the intersection of the optical axis of a camera with the image plane. It is the point on the image plane where the

The nadir is the point on the Earth’s surface directly below the observer. The isocenter is the point on the image plane where the optical axis intersects the image plane at an angle of 45 degrees. The plumb point is the point on the image plane where the plumb line intersects the image plane.

The principal point is the most important point in a camera because it is used to calculate the focal length of the camera and to correct for lens distortion. The nadir, isocenter, and plumb point are not as important as the principal point.