Q31. Back sight at station A = 0.865 m, Height of Instrument = 561.365 m. Find RL of A.
Difficulty: Easy
A. 560.500
B. 558.705
C. 559.260
D. 560.550
Correct Answer: A. 560.500 mSolution:RL = HI − BS = 561.365 − 0.865 = 560.500 m. Rearranging HI = RL + BS gives RL = HI − BS.
Q32. Rise and fall method of computation provides an arithmetic check on:
Difficulty: Easy
A. back sight and intermediate sight
B. fore sight and intermediate sight
C. back sight, intermediate sight and fore sight
D. fore sight and back sight
Correct Answer: C. back sight, intermediate sight and fore sightSolution:The Rise and Fall method checks ALL three types of sightings — BS, IS, and FS — through two checks: ΣBS − ΣFS = Last RL − First RL AND ΣRise − ΣFall = Last RL − First RL. The HI method only checks BS and FS.
Q33. Falling gradient levelling: successive readings 1.155, 2.74, 0.75, 1.79 m (3m staff). Correct booking order is:
Difficulty: Medium
A. BS, FS, BS, FS
B. BS, IS, BS, FS
C. BS, FS, IS, FS
D. BS, IS, FS, BS
Correct Answer: A. BS, FS, BS, FSSolution:Reading 1.155 m = BS. Second reading 2.74 m is near the 3 m staff limit on a falling slope — instrument shift is forced, so it becomes FS. After shift: 0.75 m = BS (new setup). 1.79 m = FS. No intermediate sights; booking: BS, FS, BS, FS.
Q34. Hand signal ‘movement of right arm by 30°’ at a construction site means:
Difficulty: Easy
A. Move top of staff to my right
B. Move to my right
C. Move top of staff to my left
D. Move to my left
Correct Answer: A. Move top of staff to my rightSolution:A partial arm movement of 30° is a plumbing signal: ‘tilt the top of the staff to the operator's right.’ A fully extended arm means continue moving in that direction. Partial arm movement = tilt (plumb) the staff.
Q35. Staff tilted with slope 20:1, observed reading = 2.5 m. Correct reading is:
Difficulty: Hard
A. 2.8 m
B. 50/√401 m
C. 51/√399 m
D. 20/7 m
Correct Answer: B. 50/√401 mSolution:Slope 20:1 → hypotenuse = √(400+1) = √401. By similar triangles: true vertical reading = 2.5 × (20/√401) = 50/√401 m ≈ 2.497 m. The tilt reduces the true vertical reading slightly below the observed slant reading.
Q36. Which is the disadvantage of Internal Focusing Telescope?
Difficulty: Medium
A. There are two separate tubes
B. There is no movement of sliding tubes
C. The line of collimation is less affected while focusing
D. The telescope is more balanced during operation
Correct Answer: A. There are two separate tubesSolution:The internal focusing design creates a double-tube configuration (outer fixed tube + internal sliding concave lens carriage), making the interior harder to clean if moisture or dust enters. Options B, C, and D are genuine advantages of internal focusing over external focusing telescopes.
Q37. Which expression is used to calculate RL of a point (Rise and Fall method)?
Difficulty: Easy
A. Height of instrument minus back sight
B. Height of instrument plus fore sight
C. Reduced level of previous point minus fore sight
D. Reduced level of previous point minus fall
Correct Answer: D. Reduced level of previous point minus fallSolution:In the Rise and Fall method: RL(new) = RL(previous) + Rise OR RL(new) = RL(previous) − Fall. When terrain drops, the difference is a Fall; new RL = previous RL − Fall. This directly uses consecutive readings, not the Height of Instrument.
Q38. Which levelling method determines elevation difference of two quite far apart points?
Difficulty: Easy
A. Check levelling
B. Fly levelling
C. Reciprocal levelling
D. Simple levelling
Correct Answer: C. Reciprocal levellingSolution:When two points are far apart and separated by a wide obstacle (river, gorge) where the instrument cannot be placed at the midpoint, Reciprocal Levelling is used. Readings from both ends average out errors from curvature, refraction, and collimation. Differential levelling is used when the obstacle is not present.
Q39. Correction of length due to reduction to mean sea level is:
Difficulty: Medium
A. directly proportional to measured length
B. directly proportional to radius of the earth
C. inversely proportional to measured length
D. inversely proportional to height above mean sea level
Correct Answer: A. directly proportional to measured lengthSolution:MSL correction = (h/R) × D. Since D (measured length) is in the numerator, the correction is directly proportional to D. It is also directly proportional to h (height above MSL) and inversely proportional to R (Earth's radius).
Q40. Calculate refraction correction (m) for a distance of 500 m.
Difficulty: Medium
A. 0.0028
B. 0.0056
C. 5.61
D. 2850
Correct Answer: A. 0.0028 mSolution:D = 500 m = 0.5 km. Cr = 0.0112 × D² = 0.0112 × 0.25 = 0.0028 m. Verification: Cc = 0.0785 × 0.25 = 0.0196 m; Cr = Cc/7 = 0.0196/7 = 0.0028 m ✓.
Q41. BM RL=100 m, BS=1.34 m; staff at A (2 km away)=2.56 m. Find true RL of A after curvature and refraction correction.
Difficulty: Hard
A. 98.51 m
B. 99.78 m
C. 99.05 m
D. 101.3 m
Correct Answer: C. 99.05 mSolution:HI = 100 + 1.34 = 101.34 m. Combined correction at 2 km: Cc = 0.0673 × 4 = 0.2692 m (subtract from reading). Corrected reading = 2.56 − 0.2692 = 2.2908 m. True RL(A) = 101.34 − 2.2908 = 99.049 ≈ 99.05 m.
Q42. Horizontal distance formula for anallatic telescope (S = staff intercept, K and C are constants):
Difficulty: Medium
A. K/S
B. 100C
C. S
D. 100S
Correct Answer: D. 100SSolution:For an anallatic telescope, K = 100 and C = 0. The general formula D = KS + C becomes D = 100S + 0 = 100S. The anallatic lens eliminates the additive constant and fixes the multiplying constant at exactly 100.
Q43. What should be the height (m) of a lighthouse to be visible from 3 km?
Difficulty: Medium
A. 0.101 m
B. 0.605 m
C. 0.673 m
D. 0.707 m
Correct Answer: B. 0.605 mSolution:h = 0.0673 × d² = 0.0673 × 9 = 0.6057 ≈ 0.605 m. This equals the combined curvature and refraction correction — the minimum height needed for the lighthouse to be visible above the Earth's curved surface at 3 km.
Q44. The difference between the last RL and first RL equals:
Difficulty: Easy
A. difference between the sum of back sights and intermediate sights
B. difference between the sum of back sights and RL of benchmark
C. difference between the sum of back sights and foresights
D. difference between the sum of back sights and height of instrument
Correct Answer: C. difference between the sum of back sights and foresightsSolution:Arithmetic check formula: ΣBS − ΣFS = Last RL − First RL. This is derived from telescoping the HI and RL equations; all intermediate computations cancel out, leaving only the net difference between total BS and total FS.
Q45. Refraction correction for distance ‘D’ between staff and instrument is proportional to:
Difficulty: Easy
A. inversely proportional to D
B. proportional to D
C. proportional to square of D
D. proportional to square root of D
Correct Answer: C. proportional to square of DSolution:Cr = 0.0112 × D² (D in km). Since D appears squared, the refraction correction is proportional to D². If D doubles, the correction quadruples. Both curvature and refraction corrections are proportional to D².
