MCQs on Chain Surveying

Correct Answer: D. 449.4 m

Solution:

A standard 30 m chain has 150 links (1 link = 0.2 m).
The chain is short by 0.2 links. Error in length = 0.2 links × 0.2 m/link = 0.04 m.
Actual length of chain (L') = 30 m - 0.04 m = 29.96 m.
Designated length of chain (L) = 30 m.
Measured length = 450 m.
True Length = (L'/L) × Measured Length = (29.96 / 30) × 450 = 449.4 m.

Correct Answer: C. Obstacle to plotting

Solution:

Obstacles in chain surveying are physical obstructions in the field that affect the process of measuring (chaining) or seeing (ranging). Plotting is the process of drawing the survey on paper, which is done after the fieldwork is complete. Therefore, an "obstacle to plotting" is not a field obstacle encountered during chaining.

Correct Answer: C. Pull

Solution:

Corrections for sag, slope, and wrong alignment are always negative because they result in a measured length that is longer than the true length. The pull (or tension) correction can be positive, negative, or zero. It is positive if the pull applied is greater than the standard pull, and negative if it is less.

Correct Answer: A. is always negative

Solution:

When a tape is not aligned in a straight line between two points, the measured distance will always be greater than the true straight-line distance. Therefore, the correction to get the true distance must always be negative (subtracted from the measured distance).

Correct Answer: C. Revenue chain

Solution:

The Revenue chain is 33 feet long and divided into 16 links. It was historically used in India for cadastral surveys, which are surveys of property boundaries, especially for land registration and taxation purposes. Gunter's chain is 66 feet long.

Correct Answer: C. Perpendicular and oblique

Solution:

Offsets are lateral measurements taken from a survey line to locate points or features. They are classified based on their angle to the survey line: Perpendicular (at 90°) and Oblique (at any other angle).

Correct Answer: C. 2 and 3

Solution:

Cumulative errors build up in the same direction. Their magnitude is generally proportional to the length of the line being measured (Statement 2), and they can be either positive (making the measurement too long) or negative (making it too short) (Statement 3).

Correct Answer: A. Rise in temperature

Solution:

Error = Measured Value - True Value. A rise in temperature causes the chain to expand, making it longer than its standard length. A longer chain under-measures the true distance (the measured value is less than the true value), resulting in a negative error. Sag and misalignment always cause positive errors (measured value > true value).

Correct Answer: B. 71.63

Solution:

The maximum permissible error on drawing paper is typically taken as 0.25 mm or 0.025 cm.
Maximum error on ground = 0.025 cm × (100 m / 1 cm) = 2.5 m.
The error in length due to an angular error is given by e = L sin(θ).
So, L = e / sin(θ) = 2.5 m / sin(2°) ≈ 71.63 m.

Correct Answer: C. Prism square

Solution:

A prism square is an optical instrument specifically designed for accurately and quickly setting out right angles (90°) to a survey line. A clinometer measures vertical angles, an offset rod measures short distances, and a plumb bob establishes a vertical line from a point.

Correct Answer: B. 36.8 kg

Solution:

Normal pull is the pull at which the correction for pull and the correction for sag cancel each other out.
Let Pn be the normal pull. Total weight of tape (W) = 20 gm/m * 20 m = 400 gm = 0.4 kg.
Pull Correction = (Pn - P_standard) * L / (A * E)
Sag Correction = -W² * L / (24 * Pn²)
Setting them equal: (Pn - 30) * 20 / (0.5 * 2100000) = (0.4)² * 20 / (24 * Pn²)
Simplifying gives a cubic equation for Pn. Solving it yields Pn ≈ 36.8 kg.

Correct Answer: B. 100

Solution:

In a standard metric chain, each link is 20 cm (0.2 m) long. Therefore, a 20-metre chain has 20 m / 0.2 m/link = 100 links.

Correct Answer: C. 0.15

Solution:

A slope of 1:10 means for every 10 units horizontal, there is 1 unit vertical. The slope angle θ = tan⁻¹(1/10).
The required horizontal distance (true length) is Lcos(θ).
The measured slope distance is L.
Hypotenusal allowance = L(sec(θ) - 1).
For small angles, this can be approximated as L * h²/ (2L²) = h²/(2L) = (3)² / (2*30) = 0.15 m. (Using h=3 for L=30 at 1:10 slope)

Correct Answer: C. Length of Gunter's chain is 66 ft.

Solution:

Standard lengths of survey chains are:
- Gunter's Chain: 66 ft (100 links)
- Engineer's Chain: 100 ft (100 links)
- Revenue Chain: 33 ft (16 links)

Correct Answer: A. Centre to centre distance between the last end of links

Solution:

The specified length of a survey chain is measured from the outside of the handle at one end to the outside of the handle at the other. This corresponds to the center-to-center distance between the first and last links. The other options relate to levelling, not distance measurement with a chain.