What is the primary purpose of levelling in surveying?
B
Determine horizontal distances
C
Determine elevation differences
D
Mark property boundaries
Analysis & Theory
Levelling is used to determine the elevation of points relative to a datum.
Which of the following instruments is used in levelling?
Analysis & Theory
The dumpy level is the most commonly used instrument for levelling.
A staff reading taken at a known elevation point is called:
Analysis & Theory
Backsight (BS) is the first reading from a known RL to establish the instrument height.
What is the elevation of the line of sight known as?
Analysis & Theory
Height of instrument (HI) = RL + Backsight.
What does the term ‘reduced level’ refer to?
B
Vertical distance from datum
C
Distance from base line
D
Corrected compass angle
Analysis & Theory
Reduced level is the elevation of a point above or below the reference datum.
Which of the following is a type of levelling?
A
Trigonometric levelling
Analysis & Theory
Trigonometric levelling determines elevation using vertical angles and distances.
A temporary benchmark is:
A
Established by survey department
B
Used for a short duration project
C
A fixed elevation reference point
D
Always located at sea level
Analysis & Theory
Temporary benchmarks are used during specific projects and are not permanent.
An error due to improper levelling of instrument is called:
Analysis & Theory
Collimation error occurs when the line of sight is not truly horizontal.
The difference in elevation between two points is found by:
B
Subtracting their staff readings
Analysis & Theory
Elevation difference = RL of one point − RL of the other.
Which method of levelling is most accurate?
Analysis & Theory
Reciprocal levelling reduces errors by taking readings in both directions.
The arithmetic check for levelling is:
B
∑BS − ∑FS = Last RL − First RL
Analysis & Theory
The basic check ensures the difference in backsight and foresight equals net RL change.
What is the ‘line of collimation’?
A
Horizontal line of sight
D
Line joining benchmarks
Analysis & Theory
The line of collimation is the line of sight of the level instrument.
What is used to measure vertical distances in levelling?
Analysis & Theory
Staff readings determine vertical heights relative to the instrument.
What does a negative RL indicate?
Analysis & Theory
Negative RLs are for points located below the reference datum.
A point with known elevation is called a:
Analysis & Theory
Benchmarks are fixed points of known elevation used for reference.
The process of finding RL using HI is:
A
RL = HI − staff reading
B
RL = HI + staff reading
Analysis & Theory
RL = Height of Instrument − staff reading (for FS and IS).
Which of the following is NOT a temporary adjustment of a level?
Analysis & Theory
Permanent adjustments are for instrument calibration and are not done daily.
Differential levelling is used to:
C
Find difference in elevation between two points
Analysis & Theory
Differential levelling helps find height differences between distant points.
In a level book, a foresight is always:
Analysis & Theory
Foresight (FS) is subtracted from HI to find RL.
Error due to curvature of Earth in long sights is a:
Analysis & Theory
Natural errors include curvature and refraction which affect distant readings.
Which levelling is used in construction of roads and railways?
Analysis & Theory
Profile levelling provides elevations along a longitudinal section for design and construction.
The difference between HI method and Rise & Fall method is:
B
Rise & Fall method gives RL directly
C
HI method is less accurate
D
Rise & Fall checks each change
Analysis & Theory
Rise & Fall method checks each elevation change and provides better error control.
Which method is suitable for uneven terrain?
Analysis & Theory
Rise & Fall method is detailed and preferred for uneven terrains.
Which is NOT an error in levelling?
A
Incorrect staff reading
Analysis & Theory
Chain sag is an error in linear measurement, not levelling.
Parallax error occurs due to:
B
Misalignment of cross-hair and image
Analysis & Theory
Parallax is caused when image and crosshairs are not in the same focal plane.
Turning point in levelling is a point where:
Analysis & Theory
Turning points are used when the instrument position is changed.
Check levelling is carried out to:
C
Verify previous levelling
Analysis & Theory
Check levelling verifies the accuracy of earlier levelling operations.
Which part of dumpy level helps in focusing the image?
Analysis & Theory
The focusing screw adjusts the clarity of the image.
A reading taken on a staff at the far side of a river for levelling is best done using:
Analysis & Theory
Reciprocal levelling reduces errors caused by refraction and curvature over long distances.
If sum of Rise = 4.00 and sum of Fall = 2.50, the difference in RL is:
Analysis & Theory
Net change = Rise – Fall = 4.00 – 2.50 = 1.50.