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Principle methods of levelling

Short answer

Methods: direct (spirit), trigonometric, barometric, hypsometric, and stadia levelling. In direct levelling, a level sets a horizontal line of sight; staff readings on points give HI = RL+BS, and RL = HI−reading. The arithmetic check ΣBS−ΣFS = last RL−first RL verifies the reduction.

List the principle methods of levelling and describe any one method.

Principle methods of levelling

  1. Direct (spirit) levelling: staff readings with a level.
  2. Trigonometric levelling: from the vertical angle and the distance.
  3. Barometric levelling: from the atmospheric pressure.
  4. Hypsometric (boiling point) levelling: from the boiling point of water.
  5. Stadia levelling (tacheometric) and GPS/total station levelling are also used in modern work.

Direct (spirit) levelling

The differences in level are found with a level and a vertical staff. A horizontal line of sight is obtained from the level.

  1. Set the level at a convenient point, level it with the foot screws and bubble.
  2. The BS is read on a BM of known RL; the HI is found: HI=RL+BSHI = RL + BS.
  3. The staff is held at the other points (IS), and finally the FS is read at a change point; RL=HI−staff readingRL = HI - \text{staff reading}.
  4. The instrument is moved ahead; the staff stays at the CP and a new BS is taken. The process continues up to the last point.
  5. The readings are booked in a level field book and checked: ΣBS−ΣFS=last RL−first RL\Sigma BS - \Sigma FS = \text{last RL} - \text{first RL}.

It is the most accurate method and is used for fixing benchmarks, roads, canals, and building sites.

✓ Answer checked by Claude Opus 5.5 (high effort)

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