---
title: "Personal errors in levelling"
subject: "Surveying I"
chapter: 5
key: "semester_3/surveying_i:personal-errors-in-leveling"
source: https://www.bctengineer.com/q/semester_3/surveying_i/personal-errors-in-leveling
site: BCT Engineering
---

# Personal errors in levelling

Surveying I · Chapter 5: Leveling

- Asked in: 2072 Chaitra, 2 marks
- Video: [Errors in Leveling - Levelling and Its Application - Surveying 1](https://www.youtube.com/watch?v=b3h_czrxzVA) — Ekeeda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/surveying_i/personal-errors-in-leveling
- Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-5

## Question

Explain personal errors in levelling.

## Short answer

Personal errors: bubble not centred, staff not held vertical (reading too high), parallax, wrong reading/booking, staff not on same change point, moving tripod/staff, calculation mistakes. Avoid by careful centring, waving staff, checking bubble, and arithmetic checks.

## Answer

Personal errors are mistakes or errors caused by the surveyor or the staff holder, not by the instrument or the weather.

- **Bubble not centred** exactly at the time of the reading, or the instrument not levelled properly.
- **Staff not held vertical** (leaning forward or backward), so the reading is too high; it can be avoided by waving the staff and taking the least reading or by using a staff bubble.
- **Parallax** from improper focusing of the eyepiece and the objective.
- **Wrong reading** of the staff (e.g. reading a wrong metre/decimetre figure, or reading an inverted staff), and wrong **booking** in the field book.
- **Staff not held on the same point** at the change point when the level is shifted.
- **Moving the staff** or the tripod during observations.
- **Calculation mistakes** while reducing the levels.

They are avoided by careful observation, checking the bubble before each reading, and using the arithmetic checks.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Personal errors are caused by:
   A. The surveyor or staff holder
   B. The instrument
   C. The weather
   D. The earth's curvature
   Answer: A. They arise from human mistakes in handling, reading or booking. (Key point: Definition)

2. If the staff leans, the reading is:
   A. Too high; cured by balancing sights
   B. Too high; reduced by waving the staff and taking the least reading
   C. Too low
   D. Unaffected
   Answer: B. A tilted staff gives a longer reading; the least reading while waving is the vertical one. (Key point: Staff not vertical)

3. What personal error occurs at a change point?
   A. Collimation error
   B. Curvature
   C. Staff not held on the same point for FS and BS
   D. Wrong graduation
   Answer: C. The FS and BS must be on exactly the same point. (Key point: Change point error)

## Related in Surveying I

- [Levelling methods; errors eliminated by balancing](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aprinciple-methods-leveling-balancing-sight) — Surveying I, chapter 5, asked 2×
- [Reciprocal levelling: why and formula](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Areciprocal-leveling-derivation) — Surveying I, chapter 5, asked 3×