GATE-2018 (24) :Wyllie – Time average equation

CSIR-NET 2014

96. Assume that a vertical photograph was taken at a flying height of 2500m above sea level by a camera with a lens of focal length 152mm. Determine the scale of photograph of the terrain whose average surface elevation is 980m. 

A) 1:50,000                 

B) 1:20,000               

C) 1:10,000               

D) 1:5,000

Focal length (f) = 152 mm

flying height ( H) = 2500 m

surface elevation (h_avg) =980 m

Scale = f / (H- h_avg) -----------------(1)

Scale = 152 / (2500-980)

         = 152 mm / 1520 m ( 1m = 1000mm)

         = 152 / 1520000

 Scale = 1: 10,000