A section line AB appears to be 10.18 cm on photograph, for which the focal length is 18 cm. The corresponding line measures 2.68 cm on a map, which is to a scale of 1/50000. The terrain has an average elevation of 210 m above the sea level. The flying altitude of the aircraft above the sea level when the photo was taken is :

Concept:

The scale of a Photograph:
The scale of a photograph depends on the flying height of the photograph, the focal length of the camera an the elevation of ground level with respect to mean sea level.

Where,

f = Focal length of a camera

H = Flying height

h = Elevation of object or ground level above M.S.L

The scale of the map is given by

Calculation:

Given, Focal length, f = 18 cm

Photo distance = 10.18 cm

Map distance = 2.68 cm

The average elevation of the terrain, H_a = 210 m

Let the height of the aircraft be H meter.

Scale, S_map = 1/50,000

We know that,

Ground distance = 134000 cm = 1340 m

Also

The scale of the photo is

H = 2579.35 m

Hence, The flying altitude of the aircraft above sea level when the photo was taken is 2579.35 m.