Question

For a constant flying height, the average scale of an aerial photograph depends on which of the following parameter(s)?

• A. Focal length of the camera
• B. Size of the photograph
• C. Size of the objects in the area
• D. Topography of the ground

Hint:

For vertical aerials: local scale \(S\approx f/(H-h_g)\). Fix \(H\) and think “change \(f\) or change \(h_g\).” Photo size or object sizes do not enter the scale formula.

Answer 1

The Correct Option is A

The photographic scale at a ground point is \(S=\dfrac{f}{H-h_g}\), where \(f\) is camera focal length, \(H\) is flying height above datum, and \(h_g\) is ground elevation at that point.
With constant \(H\), the average scale over the area depends on:
\(\bullet\) \(f\) — longer focal length $⇒$ larger scale (less reduction).
\(\bullet\) Ground elevations \(h_g\) — relief/topography causes local scale changes; the average depends on terrain heights.
It does not depend on the photo’s physical size or on “size of objects.” Hence (A) and (D) only.
\[ \boxed{\text{Correct: (A), (D)}} \]