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GATE 2017 CE (CE2) – Question 48

Geomatics Engineering · Photogrammetry: scale, flying height, parallax, camera calibration · 2 marks · Numerical answer

Vertical towers A and B stand on horizontal ground. On the aerial photograph shown, their relief displacements are 1.5 and 2.0 cm, and distances of their top images from the principal point are 4 and 6 cm respectively. If B is 80 m high, A is ______ m high.

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Correct answer: 89 to 91

Explanation

Relief displacement obeys $d/r=h/H$, with r measured to the top image. From B, $H=80(6)/2=240$ m. Thus tower A has height $240(1.5)/4=90$ m.