Why this topic is important for ECET?
Levelling is one of the most scoring topics in ECET Civil Engineering. Around 2–3 questions are consistently asked from Levelling instruments, RL calculations, methods (HI & Rise & Fall). A clear understanding of Dumpy level and Auto level helps in both theory and numerical problems.
📘 Concept Notes
1. Definition of Levelling
- Levelling is the process of finding the relative heights (RLs) of points on the earth’s surface with respect to a datum (usually Mean Sea Level).
- Used in road design, canal works, building foundations.
2. Instruments
(a) Dumpy Level
- Rigid, non-adjustable telescope fixed to its supports.
- Requires precise temporary adjustments.
- Very accurate but time-consuming.
(b) Auto Level
- Self-leveling using compensator mechanism.
- Faster, reduces human error.
- Preferred for modern surveying.
3. Terms in Levelling
- Reduced Level (RL): Elevation of a point above/below datum.
- Back Sight (BS): First reading taken on BM (benchmark).
- Fore Sight (FS): Last reading taken before shifting instrument.
- Intermediate Sight (IS): Readings between BS and FS.
- Height of Instrument (HI): Level of line of sight.
4. Methods of Levelling
(a) Height of Instrument (HI) Method
(b) Rise and Fall Method
- Difference between consecutive staff readings is calculated.
- If second reading > first → Fall.
- If second reading < first → Rise.
- RL is adjusted accordingly.
Check for arithmetic:
5. Example (HI Method)
- BM RL = 100 m, BS = 2.5 m.
FS = 1.8 m → RL = 102.5 – 1.8 = 100.7 m.
⚙️ Formulas
🔟 10 MCQs
Q1. Levelling is mainly used to determine:
a) Horizontal distance
b) Elevation of points
c) Angles
d) Bearings
Q2. In HI method, RL is found by:
a) BS – FS
b) HI – FS
c) FS – HI
d) BS + FS
Q3. BM has RL = 100 m, BS = 2.2 m, FS = 1.5 m. RL of point = ?
a) 100.7 m
b) 101.5 m
c) 101.7 m
d) 102.2 m
Q4. Which instrument uses compensator mechanism?
a) Dumpy level
b) Auto level
c) Tilting level
d) Plane table
Q5. Arithmetic check of rise & fall method is:
a) ΣBS – ΣFS = ΣRise + ΣFall
b) ΣBS – ΣFS = Last RL – First RL
c) ΣBS + ΣFS = Last RL – First RL
d) None
Q6. Which is more time-consuming but more accurate?
a) Auto level
b) Dumpy level
c) Plane table
d) Theodolite
Q7. BM RL = 150 m, BS = 2.0 m, IS = 1.6 m. HI = ? RL of IS = ?
a) HI = 152 m, RL = 150.4 m
b) HI = 148 m, RL = 149.6 m
c) HI = 152 m, RL = 151 m
d) HI = 150 m, RL = 151.6 m
Q8. Rise and Fall method is considered:
a) More accurate than HI method
b) Less accurate than HI method
c) Same accuracy
d) Used only in rough survey
Q9. Which sight is taken first from an instrument station?
a) Fore sight
b) Intermediate sight
c) Back sight
d) None
Q10. A levelling staff reading increases from 1.2 m to 2.0 m on moving forward. The ground has:
a) Rise of 0.8 m
b) Fall of 0.8 m
c) No change
d) Rise of 2.0 m
✅ Answer Key
| Q | Answer |
|---|---|
| 1 | b |
| 2 | b |
| 3 | a |
| 4 | b |
| 5 | b |
| 6 | b |
| 7 | a |
| 8 | a |
| 9 | c |
| 10 | b |
🧠 Explanations
- Q1: Levelling is done for elevations → (b).
- Q2: RL = HI – FS → (b).
- Q3: HI = 100 + 2.2 = 102.2; RL = 102.2 – 1.5 = 100.7 → (a).
- Q4: Auto level has compensator → (b).
- Q5: Check equation: ΣBS – ΣFS = Last RL – First RL → (b).
- Q6: Dumpy level needs precise adjustments → (b).
- Q7: HI = 150 + 2 = 152; RL(IS) = 152 – 1.6 = 150.4 → (a).
- Q8: Rise & fall method cross-checks calculations, hence more accurate → (a).
- Q9: First sight is always BS → (c).
- Q10: Higher reading means ground falls → Fall = 0.8 → (b).
🎯 Motivation / Why Practice Matters
In ECET 2026 Civil, Levelling is a scoring area where small mistakes in signs or formula application can lead to losing easy marks. By practicing HI & Rise & Fall problems, you can increase accuracy and speed, ensuring you don’t lose out on questions that most students get wrong under pressure.
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