GATE 2026 CE (CE1) – Question 35
The height of the plane of collimation of a levelling instrument is 100.000 m from a datum. The levelling instrument measures a Back Sight of 1.500 m on a vertically held staff at a ground point $P$. The reduced level (in m) of the ground point $P$ with respect to the datum is ______________ (*rounded off to three decimal places*).
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Show answer and explanation
Correct answer: 98.01 to 98.99
Explanation
The reduced level of a point is the height of the plane of collimation minus the staff reading, so $100.000 - 1.500 = 98.500$ m.