# Civil Engineering - UPSC Civil Service Exam Questions - Discussion

Discussion Forum : UPSC Civil Service Exam Questions - Section 2 (Q.No. 5)
5.
A 3000 m long line lying at an elevation of 450 m measures 10 cm on a vertical photograph.
The focal length of the camera is 21 cm. The scale of the photograph for the area having an elevation of 1000 m will be
1 : 27381
1 : 25008
1 : 20606
1 : 30421
Explanation:
No answer description is available. Let's discuss.
Discussion:
5 comments Page 1 of 1.

Hamza Manzoor said:   8 months ago
Scale = 10/(3000 *100) = 1/30000.
Now,
1/30000 = 0.21/(H - 450).
You get flying height, H = 6750m.

For 2nd case.
Scale = f/(H - h).
Scale = 0.21/(6750 - 1000) = 1 in 27381.
(3)

Rashid Shahab said:   3 years ago
For 1st case.
Scale = 10/(3000 *100) = 1/30000.
Now,
1/30000 = 0.21/(H - 450).
You get flying height, H = 6750m.

For 2nd case.
Scale = f/(H - h).
Scale = 0.21/(6750 - 1000) = 1 in 27381.
(2)

Manish k soni said:   5 years ago
Give an explanation of the solution.
(1)

Sam said:   5 years ago
Here, S = f/(H-h).
(1)

Patel bhai said:   6 years ago