71. If f is the focal length of the camera lens and 0 is the angle of tilt, the distance of the plumb point from the principal point will be

A. f sin 0

B. f cos 0

C. f tan 0

D. f sec 0.

72. The ratio of distances of the plumb point and the isocentre from the principle point of a vertical photograph, is

A.1

B.2

C.3

D.-4

73. From the principal point the horizon point lies on the principal line at a distance of

A. f tan 0

B. f sin 0

C. f cot 0

D. f cos O.

74. The product of the distances of plumb point and horizon point of a vertical photograph from its principal point, is

A. f 2

B. 2f

C. 3f 2

D. -1 f2

75. The height displacement on a vertical photograph

A. increases as the horizontal distance increases from the principal point

B. increases as the ground elevation increases

C. decreases as the flying height increases

D. all the above.

76. On vertical photographs, height displacement is

A. positive for points above datum

B. negative for points below datum

C.zero for points vertically below the air station

D. all the above.

77. If the image of a triangulation station of R.L. 500 m is 4 cm from the principal point of a vertical photo taken from an altitude of 2000 m, above datum, the height displacement will be

A. 2 mm

B. 4 mm

C. 6 mm

D. 10 mm.

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