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GATE 2026 CE (CE2) – Question 26

Geomatics Engineering · Principles of surveying: plane and geodetic surveying, errors and adjustment · 1 mark · Multiple choice

Which one of the following statements is TRUE with respect to levelling survey?

  1. A level surface at all points is normal to the direction of the force of gravity.
  2. Two level surfaces can cross each other.
  3. Ellipsoid is an irregular surface approximating the physical surface of the Earth.
  4. Geoid is a regular surface approximating the physical surface of the Earth.

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Show answer and explanation

Correct answer: (A) A level surface at all points is normal to the direction of the force of gravity.

Explanation

A level surface is an equipotential surface of gravity, so it is perpendicular to the plumb line at every point. Two level surfaces cannot cross, because the potential would then have two values at one point. The geoid is the irregular level surface that approximates mean sea level, and the ellipsoid is the regular mathematical surface, so options C and D have them the wrong way round.