Q46. Calculate corrected staff reading at point A if instrument is 1.5 km away and observed reading is 3.46 m.
Difficulty: Medium
A. 3.28 m
B. 3.3 m
C. 3.43 m
D. 3.48 m
Correct Answer: B. 3.3 mSolution:Combined correction = 0.0673 × 1.5² = 0.0673 × 2.25 = 0.1514 m. Corrected reading = 3.46 − 0.1514 = 3.3086 ≈ 3.3 m.
Q47. Which is true for the correction for curvature?
Difficulty: Medium
A. Proportional to distance between staff and instrument
B. Always negative and proportional to square of distance
C. Always positive and proportional to square of distance
D. Always positive and proportional to distance
Correct Answer: B. Always negative and proportional to square of distanceSolution:Curvature makes staff readings appear too large (correction must be subtracted → negative). Cc = 0.0785 × D² (D in km). It is proportional to D², not D. The correction is always negative (must be subtracted from observed reading).
Q48. BM RL=150 m, BS=1.56 m; inverted FS at A=1.65 m. Calculate RL of point A.
Difficulty: Medium
A. 146.79 m
B. 149.91 m
C. 152.8 m
D. 153.21 m
Correct Answer: D. 153.21 mSolution:HI = 150 + 1.56 = 151.56 m. Inverted FS = −1.65 m. RL(A) = 151.56 − (−1.65) = 151.56 + 1.65 = 153.21 m. The overhead target (inverted staff) has RL above HI.
Q49. The ratio of focal length of the objective to stadia interval is called:
Difficulty: Easy
A. additive factor
B. multiplying factor
C. staff intervals
D. subtractive factor
Correct Answer: B. multiplying factorSolution:In stadia tachymetry, D = KS + C. K = f/i (focal length / stadia interval) = the multiplying factor (typically 100). C = f + d = additive constant. The ratio f/i is specifically called the multiplying factor.
Q50. The height of any point with respect to mean sea level is called:
Difficulty: Easy
A. Bench mark
B. Datum
C. Level surface
D. Reduced level
Correct Answer: D. Reduced levelSolution:Reduced Level (RL) is the vertical elevation of a point measured relative to an established datum (usually MSL). A Bench Mark is a point of known RL; Datum is the reference surface itself; Level surface is a curved equipotential surface.
Q51. Staff at A = 2.8 m, staff at BM = 2.5 m, RL of BM = 100 m. Calculate RL of A.
Difficulty: Easy
A. 97.22 m
B. 99.7 m
C. 100.3 m
D. 105.3 m
Correct Answer: B. 99.7 mSolution:HI = RL of BM + BS = 100 + 2.5 = 102.5 m. RL(A) = HI − Staff at A = 102.5 − 2.8 = 99.7 m. Cross-check: Fall = 2.8 − 2.5 = 0.3 m; RL(A) = 100 − 0.3 = 99.7 m ✓.
Q52. Staff lower reading=1.4 m, upper=2.9 m; anallatic lens tacheometer. Find horizontal distance.
Difficulty: Medium
A. 100 m
B. 140 m
C. 150 m
D. 200 m
Correct Answer: C. 150 mSolution:Staff intercept S = 2.9 − 1.4 = 1.5 m. With anallatic lens: K = 100, C = 0. D = 100 × 1.5 = 150 m.
Q53. What is the correct ratio of refraction correction to curvature correction?
Difficulty: Easy
A. 1/4
B. 1/6
C. 1/7
D. 1/9
Correct Answer: C. 1/7Solution:Refraction correction Cr = 0.0112D²; Curvature Cc = 0.0785D². Ratio = 0.0112/0.0785 = 1/7. From first principles: Cr = D²/(14R) and Cc = D²/(2R), so Cr/Cc = 2/14 = 1/7.
Q54. Calculate curvature correction (m) for a distance of 500 m.
Difficulty: Medium
A. 0.0196 m
B. -0.9196 m
C. 0.0028 m
D. -0.0028 m
Correct Answer: A. 0.0196 mSolution:D = 500 m = 0.5 km. Cc = 0.0785 × D² = 0.0785 × 0.25 = 0.01963 ≈ 0.0196 m (magnitude). Note: 0.0028 m is the refraction correction (option C/D), not curvature.
Q55. Which of the following is correct for sensitivity of the bubble tube?
Difficulty: Medium
A. Sensitivity decreases with increase in internal radius of the tube
B. Sensitivity decreases with increase in diameter of the tube
C. Sensitivity increases with decrease in length of the tube
D. Sensitivity increases with decrease in viscosity of the liquid
Correct Answer: D. Sensitivity increases with decrease in viscosity of the liquidSolution:Lower viscosity = less internal friction = bubble moves more readily for a given tilt = higher sensitivity. Options A, B, C are all wrong: larger radius, larger diameter, and longer bubble all INCREASE sensitivity.
Q56. What is the correct sequence of temporary adjustment of level?
Difficulty: Easy
A. Centering, leveling and setting
B. Leveling, setting and centering
C. Setting, centering and leveling
D. Setting, leveling and centering
Correct Answer: C. Setting, centering and levelingSolution:Correct sequence: (1) Setting up the tripod at the station; (2) Centering the instrument over the station mark (optical plummet); (3) Levelling using foot screws and bubble tube; followed by (4) Focussing before each reading.
Q57. Reciprocal levelling eliminates:
Difficulty: Easy
A. Collimation error only
B. Collimation, curvature and refraction error
C. Curvature and refraction error only
D. Curvature error fully and refraction error partly
Correct Answer: B. Collimation, curvature and refraction errorSolution:Reciprocal levelling takes readings from both ends of the line and averages the two apparent differences. This automatically cancels: (1) collimation error (line of sight not horizontal), (2) earth curvature, and (3) atmospheric refraction — because these systematic errors appear equally in both setups.
Q58. Calculate combined correction for curvature and refraction (m) for distance of 2 km.
Difficulty: Easy
A. 0.045 m
B. 0.135 m
C. 0.269 m
D. 3.14 m
Correct Answer: C. 0.269 mSolution:Combined Cc = 0.0673 × D² = 0.0673 × 4 = 0.2692 m ≈ 0.269 m. (Curvature 0.0785 × 4 = 0.314 m; refraction 0.0112 × 4 = 0.045 m; net = 0.269 m.)
Q59. Reciprocal levelling across pond: setup A — staff(A)=2.5, staff(B)=2.0; setup B — staff(A)=1.2, staff(B)=1.7. Difference in height A and B:
Difficulty: Medium
A. 0 m
B. 0.5 m
C. 1 m
D. 1.85 m
Correct Answer: B. 0.5 mSolution:Apparent diff from A: 2.5 − 2.0 = 0.5 m (B higher). Apparent diff from B: 1.7 − 1.2 = 0.5 m (B higher). True diff = (0.5 + 0.5)/2 = 0.5 m.
Q60. The line normal to the plumb line is called:
Difficulty: Easy
A. Level line
B. Vertical line
C. Horizontal line
D. Datum line
Correct Answer: A. Level lineSolution:A level line lies within a level surface where every point is perpendicular to the local direction of gravity (plumb line). A horizontal line is a straight tangent to the level surface at one point only. A vertical line is parallel to (not perpendicular to) the plumb line.
