true vertical photograph

true vertical photograph

P in this case is photo nadir, ground nadir and the principle point of the photograph.An aerial photograph taken with the optical axis of the camera perpendicular to the ground. In such a photograph, the principal point, the ground nadir, and the photo nadir coincide. Whereas the principal point is always the geometric center of a photo, the photos other than the true verticals—the ground and photo nadir—will fall away from the principal point.