Which point is directly below the camera in aerial photography?

The nadir point is the term used to identify the point on the ground that lies directly below the camera when capturing aerial photographs. This point is crucial in aerial photography because it serves as a reference for determining the exact location on the ground that corresponds with the center of the camera's view. Understanding the nadir point is important for accurately interpreting aerial imagery and mapping, as it provides a basis for measurements and analyses related to the captured photograph.

In aerial photography, the principal point refers to the geometric center of the image but does not necessarily align directly with the ground point beneath the camera. The isocenter is related to the perspective and field of view of the image but also does not indicate the point directly below the camera. A control point is a known geographic location on the ground that is used for georeferencing but is not tied to the position of the camera itself. Thus, the nadir point is uniquely defined as the spot directly beneath the camera at the time of image capture.