Question

The flying height of a flight and average ground elevations respectively from MSL are 3.45 km and 450 m. If the focal length of the camera used is 150 mm, then the scale of the aerial photograph is

• A. 1:30000
• B. 1:25000
• C. 1:20000
• D. 1:15000

Hint:

The scale of a vertical aerial photograph is the ratio of the camera focal length \(f\) to the flying height above the ground, where the height above ground equals the flying height above MSL minus the average ground ele

Answer 1

The Correct Option is C

Concept:
The scale of a vertical aerial photograph is the ratio of the camera focal length \(f\) to the flying height above the ground, where the height above ground equals the flying height above MSL minus the average ground elevation: \(\text{Scale} = \dfrac{f}{H - h}\).

Step 1:
Find the height of the camera above the average ground. Flying height above MSL \(H = 3.45\ \text{km} = 3450\ \text{m}\) and average ground elevation \(h = 450\ \text{m}\), so the height above ground is \(H - h = 3450 - 450 = 3000\ \text{m}\).

Step 2:
Apply the scale formula with \(f = 150\ \text{mm} = 0.150\ \text{m}\): \[\text{Scale} = \frac{0.150}{3000} = \frac{1}{20000}.\]

Answer: Option (3) — 1:20000.