Determining photographic scale: A vertical photograph is taken from a flying height of 300 m above ground with a camera of focal length 15 cm. Assuming level terrain and negligible tilt, what is the photo scale?

Introduction / Context:
Photographic scale relates the focal length to the flying height above ground for vertical photos. Quick estimation of scale is vital for flight planning and for converting photo measurements to ground distances.

Given Data / Assumptions:

• Focal length f = 15 cm = 0.15 m.
• Flying height above ground H_g = 300 m.
• Flat terrain and negligible tilt; scale uniform across the photo.

Concept / Approach:
For a vertical photograph over level ground, scale S = f / H_g. The ratio should be expressed as 1 : (H_g / f). Careful unit handling is necessary to avoid order-of-magnitude errors.

Step-by-Step Solution:
Compute S = f / H_g = 0.15 / 300 = 0.0005.Express as a representative fraction: 1 : (1 / 0.0005) = 1 : 2,000.Hence, the photograph has a scale of approximately 1 : 2,000.

Verification / Alternative check:
In centimetre units: f = 15 cm, H_g = 30,000 cm; S = 15/30,000 = 1/2,000, confirming the same result.

Why Other Options Are Wrong:
1:1,500 and 1:2,500/1:3,000 are off the exact calculation; 1:10,000 would require a much higher flying height or shorter focal length.

Common Pitfalls:
Using flying height above datum instead of above ground, and failing to keep f and H in consistent units.

Final Answer:
1 : 2,000.