B. Camera

1. General

A photogrammetric camera is considerably larger and more complex than a hand-held or cell phone camera. Film as the image capture medium has been largely replaced by a digital detector array, but the general camera characteristics and terminology are the same.

Figure B-1 is stylized version of an airborne mapping camera.

Figure B-1 Aerial Camera

The film or sensor array is located on the focal plane, where the image comes to focus. At typical flying heights, the image distance and focal length are the same.

The camera uses a fixed-focus lens system, Figure B-2, due to the flying speed and and height.

Figure B-2 Lens System

The lens system's front and read nodal points, N and N', serve as the reference points for measuring object, image, and focal distances. Each light ray enters the front nodal point and emerges from the rear nodal point parallel with its original direction.

Most traditional mapping cameras used a 6.00 inch nominal focal length lens, with some as short as 3.5 inches, others up to 9 inches.