Q76. Height of instrument (HI) is calculated as:
Difficulty: Easy
A. RL of BM + BS reading
B. RL of BM – BS reading
C. RL of BM + FS reading
D. RL of BM – FS reading
Correct Answer: A. RL of BM + BS readingSolution:HI = RL of BM + BS. The Back Sight (BS) is a staff reading taken at a BM of known RL; adding it gives the elevation of the instrument's line of sight above the datum.
Q77. Foresight is:
Difficulty: Easy
A. The staff reading taken at the change point before the instrument is shifted
B. The first staff reading taken at the BM
C. A reading taken on a point of known elevation
D. A reading taken to check previous readings
Correct Answer: A. The staff reading taken at the change point before the instrument is shiftedSolution:Foresight is the last reading taken from each instrument position, on the change point (or closing BM) before the instrument moves. It closes the current HI and establishes the RL of the next CP.
Q78. The anallatic lens is used in:
Difficulty: Easy
A. Increase the magnification of the telescope
B. Eliminate the additive constant
C. Improve the quality of the image
D. Reduce the multiplying factor
Correct Answer: B. Eliminate the additive constantSolution:The anallatic lens is a fixed concave lens placed in the tacheometer telescope that makes C = 0. This simplifies the stadia distance formula to D = 100S without any additive constant to apply.
Q79. The surface of still water is an example of:
Difficulty: Easy
A. Level surface
B. Horizontal surface
C. Inclined surface
D. Datum surface
Correct Answer: A. Level surfaceSolution:Still water naturally distributes itself along an equipotential of the Earth's gravity field (a level surface). It is NOT a horizontal (flat) surface — it curves with the Earth. The geoid (mean sea level) is the ultimate reference level surface.
Q80. Length of bubble tube = 50 mm, division length = 2 mm, angle for 4 divisions = 0.007 rad. Find radius of curvature.
Difficulty: Hard
A. 28.57 m
B. 40 m
C. 57.14 m
D. 100 m
Correct Answer: C. 57.14 mSolution:R = (4 × d × L) / α = (4 × 2 × 50) / 0.007 = 400/7 = 57.14 m.
Q81. Staff at B = 1.95 m, staff at C = 1.55 m. The rise from B to C is:
Difficulty: Easy
A. 0.2 m
B. 0.3 m
C. 0.4 m
D. 1.55 m
Correct Answer: C. 0.4 mSolution:A smaller staff reading means higher ground (closer to the line of sight). Rise = staff at B − staff at C = 1.95 − 1.55 = 0.40 m. C is 0.4 m higher than B.
Q82. Reciprocal levelling: setup at A – staff(A)=1.490, staff(B)=2.195; setup at B – staff(B)=0.705, staff(A)=1.540. True height difference:
Difficulty: Medium
A. 0.705 m
B. 0.835 m
C. 0.770 m
D. 1.540 m
Correct Answer: C. 0.770 mSolution:Apparent diff from A: 2.195 − 1.490 = 0.705 m. Apparent diff from B: 1.540 − 0.705 = 0.835 m. True diff = (0.705 + 0.835)/2 = 0.770 m.
Q83. The combined correction for curvature and refraction is:
Difficulty: Easy
A. 0.0785 D²
B. 0.0673 D²
C. 0.0112 D²
D. D²/2R
Correct Answer: B. 0.0673 D²Solution:Combined correction = Curvature − Refraction = 0.0785D² − 0.0112D² = 0.0673D² (D in km, result in metres). The refraction correction (1/7 of curvature) is subtracted because it partially compensates for curvature.
Q84. To find the true difference of elevation between two points A and B, the level should be placed:
Difficulty: Medium
A. Near to A
B. At the exact midpoint of AB
C. Near to B
D. At any convenient location
Correct Answer: B. At the exact midpoint of ABSolution:At the midpoint, both staffs are equidistant from the instrument. Curvature, refraction, and collimation errors are equal for both readings and cancel in the difference. This is the principle of balancing BS and FS distances, and the basis of the two-peg test.
Q85. The two-peg test is performed to check:
Difficulty: Medium
A. The line of collimation is parallel to the axis of the bubble tube
B. The vertical axis of the instrument is truly vertical
C. The crosshairs are correctly placed in the reticle
D. The foot screws are properly adjusted
Correct Answer: A. The line of collimation is parallel to the axis of the bubble tubeSolution:The two-peg test checks that when the bubble is centred, the line of collimation is truly horizontal. This requires the line of collimation to be parallel to the bubble tube axis. If not parallel, a collimation error exists and must be corrected by adjusting the diaphragm screws.
Q86. A levelling traverse with one change point uses readings in the order:
Difficulty: Medium
A. BS, BS, FS, FS
B. FS, BS, FS, BS
C. BS, FS, BS, FS
D. BS, IS, IS, FS
Correct Answer: C. BS, FS, BS, FSSolution:Standard pattern for one-CP run: (1) BS on starting BM, (2) FS on change point, (3) BS on same change point (after instrument moves), (4) FS on closing BM. Pattern: BS → FS → BS → FS.
Q87. Upper stadia reading = 0.1095 m, lower = 0.0611 m, S = 3 m. Find horizontal distance.
Difficulty: Hard
A. 62 m
B. 55 m
C. 70 m
D. 48 m
Correct Answer: A. 62 mSolution:D = S / (upper − lower) = 3 / (0.1095 − 0.0611) = 3 / 0.0484 = 61.98 ≈ 62 m.
Q88. Statement 1: Curvature makes the object appear at a lower position. Statement 2: Refraction makes the object appear at a higher position. Which is correct?
Difficulty: Medium
A. Only Statement 1 is correct
B. Only Statement 2 is correct
C. Both statements are correct
D. Both statements are wrong
Correct Answer: C. Both statements are correctSolution:Curvature causes the ground to curve away below the line of sight, making objects appear lower (reading appears larger). Refraction bends light downward, making objects appear higher (partially compensates curvature). Both statements are independently correct.
Q89. The main advantage of the rise and fall method of levelling over the height of instrument method is that it:
Difficulty: Easy
A. Requires fewer columns in the field book
B. Provides a check on intermediate sights
C. Is faster to compute in the field
D. Does not require a benchmark
Correct Answer: B. Provides a check on intermediate sightsSolution:The rise and fall method captures every IS reading in the rise/fall column. The three-check system (ΣBS − ΣFS = ΣRise − ΣFall = Last RL − First RL) catches errors in IS readings, which the HI method's single check cannot detect.
Q90. RL of BM = 211.800 m, BS = 1.377 m, FS = 1.835 m. Find RL of the station.
Difficulty: Medium
A. 211.342 m
B. 212.200 m
C. 213.177 m
D. 210.500 m
Correct Answer: A. 211.342 mSolution:HI = 211.800 + 1.377 = 213.177 m. RL of station = HI − FS = 213.177 − 1.835 = 211.342 m.
Q91. Achromatism in a surveyor’s telescope is:
Difficulty: Easy
A. An unwanted defect that should be corrected
B. A desirable property
C. A property related to magnification only
D. Not relevant to accuracy of the instrument
Correct Answer: B. A desirable propertySolution:Achromatism means the objective lens brings all wavelengths of light to the same focus, eliminating chromatic aberration (colour fringes). This produces a sharp, clear image of the staff. An achromatic doublet (crown + flint glass) lens is used in surveying telescopes for this purpose.
