MCQs on Levelling
Q61. Fly levelling is used for:
Difficulty: Easy
Correct Answer: B. ReconnaissanceSolution:Fly levelling is a rapid, rough survey performed for reconnaissance — to check feasibility of a route before detailed levelling begins. It is not precise enough for check levelling, profile levelling, or cross-section work.
Q62. The mean sea level used by Survey of India as reference datum is the mean sea level of:
Difficulty: Easy
Correct Answer: D. MumbaiSolution:Survey of India established MSL at Mumbai (Apollo Bunder tidal gauge). All Indian GTS benchmarks and topographic maps reference this Mumbai MSL datum.
Q63. An internally focussing telescope uses:
Difficulty: Medium
Correct Answer: C. A concave lens between the objective and the eyepieceSolution:Internal focussing uses a movable concave (negative) lens placed between the objective lens and the cross-hair diaphragm. Moving this lens changes the effective focal length and brings the image into focus while keeping the tube length constant.
Q64. A level line is:
Difficulty: Easy
Correct Answer: A. Parallel to mean spheroidal surfaceSolution:A level line lies in a level surface (equipotential of gravity) and therefore runs parallel to the mean spheroidal surface everywhere along its length. It is NOT a straight line — it curves with the Earth.
Q65. The formula for curvature correction is:
Difficulty: Hard
Correct Answer: B. D²/2RSolution:The rigorous derivation gives Cc = D²/(2R). Substituting R = 6370 km gives 0.0785D² m (D in km). Some Indian textbooks simplify this differently — always follow the formula as given in your syllabus reference.
Q66. A bench mark is:
Difficulty: Easy
Correct Answer: A. A fixed point of known elevationSolution:A bench mark is a permanent physical mark (bronze disk, chiselled arrow, concrete pillar) whose Reduced Level (elevation above the datum) is precisely known and officially recorded. It serves as the starting or closing point for levelling surveys.
Q67. Geoid is the surface of:
Difficulty: Easy
Correct Answer: B. Zero elevationSolution:The geoid is the equipotential surface of the Earth's gravity field that coincides with mean sea level (MSL). By convention, its elevation (Reduced Level) = 0 everywhere. All surveying elevations are measured above or below the geoid.
Q68. The line passing through the intersection of cross hairs and the optical centre of objective lens is called:
Difficulty: Easy
Correct Answer: B. Line of collimationSolution:The line of collimation (line of sight) passes through (1) the intersection of the cross hairs and (2) the optical centre of the objective lens. When the instrument is levelled and correctly adjusted, this line must be horizontal.
Q69. The sensitivity of a bubble tube decreases when:
Difficulty: Medium
Correct Answer: D. The viscosity and surface tension of the liquid are increasedSolution:Higher viscosity causes greater internal friction that resists bubble movement. Higher surface tension creates stronger adhesion between the bubble and the tube wall. Both effects make the bubble sluggish and reduce sensitivity. Increasing tube radius, bubble length, or tube diameter all INCREASE sensitivity.
Q70. The rise and fall method of booking levels provides a check on:
Difficulty: Medium
Correct Answer: C. Both back sights and fore sightsSolution:The fundamental arithmetic check ΣBS − ΣFS = Last RL − First RL applies to both rise and fall AND HI methods. However, the rise and fall method ALSO catches errors in IS readings through the ΣRise − ΣFall check. The question asks what is guaranteed to be checked; the direct check covers both BS and FS.
Q71. In which of the following level, the telescope is rigidly fixed to the levelling head?
Difficulty: Easy
Correct Answer: A. Dumpy levelSolution:The dumpy level has its telescope permanently and rigidly attached to the levelling head. It cannot be tilted independently. Unlike the tilting level (which can be tilted via a tilting screw) or the auto level (which uses a compensator), the dumpy must be levelled using foot screws and the long bubble tube.
Q72. Differential levelling is used to find:
Difficulty: Easy
Correct Answer: D. Difference of elevation between two pointsSolution:Differential levelling is the basic technique of running a series of instrument setups and staff readings between two points to determine their difference in elevation. Change points are used when the distance is too large for a single setup.
Q73. A level line is:
Difficulty: Easy
Correct Answer: A. Parallel to mean spheroidSolution:This repeats the fundamental definition: a level line lies in a level surface, which is an equipotential surface parallel to the mean spheroid. It curves with the Earth and is always perpendicular to the local direction of gravity.
Q74. A line of levels commences with:
Difficulty: Easy
Correct Answer: C. A back sight and closes with a fore sightSolution:By convention, the first staff reading in any levelling run is taken on a point of known RL (BM or change point) and is called a Back Sight (BS). The last reading in the run is taken on the closing BM or closing change point and is called a Fore Sight (FS). The check ΣBS − ΣFS = Last RL − First RL confirms this convention.
Q75. The rise and fall method provides a check on:
Difficulty: Medium
Correct Answer: D. Back sights, intermediate sights, and fore sightsSolution:The rise and fall method captures every staff reading (BS, IS, FS) in the Rise or Fall column. The triple check (ΣBS − ΣFS = ΣRise − ΣFall = Last RL − First RL) ensures that errors in any reading type are detected. The HI method does NOT catch IS errors arithmetically.