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Bihar Special Survey Amin practice questions

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Question 1Surveying Fundamentals and Measurement

In chain surveying, which element is measured directly in the field rather than computed from other measurements?

  1. The length of each chain line between stations Correct answer.
  2. The area of each triangle
  3. The interior angles at each station
  4. The reduced level of each station

Explanation

Chain surveying depends on linear measurement only: the sides of the triangles forming the framework are measured in the field, and angles are not observed with instruments. Angles and areas are later derived from those measured lengths by geometry or trigonometry. Levels belong to levelling work, not to the chain survey framework.

Question 2Surveying Fundamentals and Measurement

A survey line is measured as 20 chains using a 20 m chain. What is the approximate length of the line in metres?

  1. 200 m
  2. 800 m
  3. 100 m
  4. 400 m Correct answer.

Explanation

A standard chain is 20 m long, so each chain unit represents 20 m of ground length. Multiplying 20 chains by 20 m per chain gives 400 m. The arithmetic is direct once the chain length is known, and no temperature or slope correction is implied here.

Question 3Surveying Fundamentals and Measurement

In a chain survey, the framework that is built up before any offsets are taken consists of which figures?

  1. Circles of equal radius
  2. Regular hexagons
  3. Parallel rectangles only
  4. Well-conditioned triangles Correct answer.

Explanation

The chain survey framework is formed by dividing the area into a network of triangles whose sides are measured directly. Triangles are preferred because a triangle is a rigid figure that cannot distort without a change in side length. Offsets and details are then located from these fixed triangle sides.

Question 4Surveying Fundamentals and Measurement

Which instrument is most appropriate for setting out a right angle at a chain station during a small-scale chain survey?

  1. Plane table
  2. Prismatic compass
  3. Cross-staff Correct answer.
  4. Dumpy level

Explanation

A cross-staff is designed specifically to set out or locate perpendiculars to a chain line, and the optical square serves the same purpose. It is a simple right-angle instrument used with the chain, which is why it suits chain survey work. The other instruments serve levelling, angular measurement, or plane tabling.

Question 5Surveying Fundamentals and Measurement

What is the primary purpose of ranging a survey line before chaining it?

  1. To measure the vertical angle of the ground slope
  2. To compute the area enclosed by the survey
  3. To fix intermediate points on the same straight line between the end stations Correct answer.
  4. To determine the magnetic bearing of the line

Explanation

Ranging establishes intermediate points that lie exactly on the straight line joining two end stations, so that each chain length can be laid along that line. Without ranging, the chain would wander and the measured length would not represent the true straight-line distance. Bearings, slope angles, and areas are separate operations.

Question 6Surveying Fundamentals and Measurement

A chain is found to be 0.1 m too long over its nominal 20 m length. A line measured with it reads 200 m. What is the true length of the line?

  1. 202 m
  2. 201 m Correct answer.
  3. 200.1 m
  4. 199 m

Explanation

The chain records fewer units than the true distance because each unit is longer than nominal. The correction factor is the actual length divided by the nominal length, that is 20.1/20 = 1.005. Multiplying 200 m by 1.005 gives a true length of 201 m.

Question 7Surveying Fundamentals and Measurement

Which correction must be applied to a measured line when the ground slopes uniformly between two stations?

  1. A correction for sag only
  2. A correction for temperature only
  3. A hypotenuse-to-horizontal correction subtracted from the measured length Correct answer.
  4. A correction for pull only

Explanation

A chain laid on sloping ground measures the slope distance, which is the hypotenuse of the right triangle formed with the horizontal. The horizontal distance is always shorter, so the slope correction is subtracted from the measured length. Temperature, sag, and pull corrections address tape behaviour, not ground slope.

Question 8Surveying Fundamentals and Measurement

Why is a hypodermic or metallic tape generally preferred over a cloth tape for precise chain survey measurements?

  1. It does not require any zero-mark adjustment
  2. It changes length less under tension and moisture Correct answer.
  3. It can be read from a greater distance
  4. It is lighter and therefore easier to carry

Explanation

Metallic and steel tapes have a low coefficient of extension and are little affected by dampness, so they hold their length better than cloth tapes. Cloth tapes stretch when wet and under pull, which introduces systematic error. Precision work therefore uses metallic or steel tapes.

Question 9Surveying Fundamentals and Measurement

A tape is standardised at 20 degrees Celsius but is used at 35 degrees Celsius. If the coefficient of thermal expansion is 1.2 x 10^-5 per degree Celsius and the measured length is 100 m, what is the temperature correction?

  1. +0.018 m Correct answer.
  2. +0.0018 m
  3. +0.180 m
  4. -0.018 m

Explanation

The correction equals measured length times coefficient of expansion times the temperature difference. Here 100 x 1.2 x 10^-5 x 15 gives 0.018 m. Because the tape is warmer than standard, it has expanded and reads short, so the correction is positive.

Question 10Surveying Fundamentals and Measurement

In the context of linear measurement, what does the term sag correction account for?

  1. The shortening of a tape due to excessive applied pull
  2. The misalignment of a tape from the survey line
  3. The lengthening of a tape due to rising temperature
  4. The shortening of a tape that dips between supports under its own weight Correct answer.

Explanation

When a tape is supported only at its ends, its own weight makes it dip into a catenary curve. The curved path is longer than the chord, so the tape reads more than the true horizontal distance, and a negative correction is applied. Sag correction depends on weight per unit length, span, and tension.

Question 11Surveying Fundamentals and Measurement

Cross-staff readings are taken to locate an object from a chain line. Which quantity is being determined by such an offset?

  1. The perpendicular distance from the object to the chain line Correct answer.
  2. The bearing of the chain line from magnetic north
  3. The elevation of the object above datum
  4. The horizontal angle between two chain lines

Explanation

An offset is a lateral measurement taken at right angles from the chain line to a detail such as a boundary or building corner. The cross-staff helps establish that right angle so the offset length is truly perpendicular. Offsets fix the position of details relative to the framework.

Question 12Surveying Fundamentals and Measurement

Which of the following is classified as a systematic error in chain surveying?

  1. A sudden gust of wind disturbing the tape
  2. Random misreading of a graduation by different surveyors
  3. A tape that is consistently 5 mm short over its whole length Correct answer.
  4. Careless booking of a reading in the field book

Explanation

Systematic errors follow a definite law and accumulate in the same direction throughout the survey, so they can be corrected by applying a computed correction. A tape that is uniformly short produces such an error. The other options are accidental or personal errors that do not follow a fixed pattern.

Question 13Surveying Fundamentals and Measurement

A line measured along sloping ground is 50 m, and the difference in elevation between its ends is 3 m. What is the horizontal distance approximately?

  1. 47.00 m
  2. 53.00 m
  3. 49.91 m Correct answer.
  4. 50.09 m

Explanation

The horizontal distance is the square root of the measured length squared minus the elevation difference squared. Here the square root of 2500 minus 9 is the square root of 2491, which is about 49.91 m. The horizontal distance is always less than the slope distance.

Question 14Surveying Fundamentals and Measurement

Which of the following best describes a well-conditioned triangle in a chain survey framework?

  1. A triangle with one angle of exactly 90 degrees
  2. A triangle whose angles lie between about 30 and 120 degrees, ideally close to equilateral Correct answer.
  3. A triangle whose longest side is measured twice
  4. A triangle with all sides equal to one chain length

Explanation

A well-conditioned triangle is one in which no angle is too small or too large, because small angular errors in plotting then produce large positional errors. Angles between roughly 30 and 120 degrees, with an equilateral shape preferred, give the most reliable framework. The shape, not the absolute size, determines conditioning.

Question 15Surveying Fundamentals and Measurement

What is the purpose of a check line in a chain survey?

  1. To establish the magnetic meridian
  2. To mark the boundary of the survey area
  3. To verify the accuracy of the framework by an independent measurement Correct answer.
  4. To replace the base line in the survey

Explanation

A check line, also called a proof line, joins two already fixed stations and is measured only to test the framework. If the measured value agrees closely with the value computed from the framework geometry, the survey is considered consistent. It does not form part of the main triangulation.

Question 16Surveying Fundamentals and Measurement

A surveyor measures a line as 120 m with a 30 m chain that is actually 30.05 m long. What is the true length of the line?

  1. 120.05 m
  2. 121.20 m
  3. 119.80 m
  4. 120.20 m Correct answer.

Explanation

The correction factor equals actual chain length divided by nominal length, that is 30.05/30 = 1.00167 approximately. Multiplying 120 m by this factor gives about 120.20 m. Because the chain is longer than nominal, the recorded distance understates the true distance.

Question 17Surveying Fundamentals and Measurement

In an obstacle-to-chaining situation where a pond blocks the line but visibility is clear across it, which method is used to find the obstructed distance?

  1. Lowering the tape into the water and reading the depth
  2. Measuring the magnetic bearing across the pond
  3. Setting out perpendiculars and using similar triangles or the sine rule Correct answer.
  4. Using a plane table to plot the pond boundary

Explanation

When a line is obstructed but both stations are visible, the distance can be found by setting out a subsidiary triangle on accessible ground and measuring its sides and angles. Similar triangles or the sine rule then yield the obstructed length. This avoids the need to chain across the obstacle itself.

Question 18Surveying Fundamentals and Measurement

A chain line is measured as 300 m at an average tension of 120 N, while the tape was standardised at 80 N. If the tape has a cross-sectional area of 2 mm squared and elastic modulus 2 x 10^5 N per mm squared, what is the pull correction?

  1. +0.300 m
  2. -0.030 m
  3. +0.030 m Correct answer.
  4. +0.003 m

Explanation

The pull correction equals the change in tension times length divided by the product of area and elastic modulus. Here 40 N times 300 m divided by 2 mm squared times 2 x 10^5 N per mm squared gives 0.030 m. Since the applied pull exceeds standard tension, the tape stretches and the correction is positive.

Question 19Surveying Fundamentals and Measurement

A survey line is measured with a tape whose zero end is worn away. What is the most appropriate field practice to avoid error?

  1. Replace the tape with a cloth tape
  2. Measure from the 1 m mark and subtract 1 m from each reading Correct answer.
  3. Ignore the wear because it is always negligible
  4. Add 1 m to each reading to compensate

Explanation

When the zero end of a tape is worn or broken, measurements are started from a sound graduation such as the 1 m mark. The offset is then subtracted from every reading so the recorded length remains correct. This is a standard practice that avoids a constant systematic error.

Question 20Surveying Fundamentals and Measurement

Which of the following best explains why ranging by eye is acceptable only for short lines?

  1. The chain cannot be straightened over long distances
  2. Long lines always cross obstacles
  3. Ranging rods are too short to be seen at long distances
  4. The angular error of direct ranging grows with distance, so the intermediate points drift off line Correct answer.

Explanation

Direct ranging by eye relies on judging alignment between rods, and the smallest perceptible angular deviation produces a lateral displacement that increases with distance. Over long lines this displacement becomes significant, so indirect ranging or an instrument is preferred. The limitation is geometric, not a matter of rod length.

Question 21Surveying Fundamentals and Measurement

What is the chief advantage of a base line in a chain survey being measured with extra care and repetition?

  1. Errors in the base line propagate into every computed dimension of the framework Correct answer.
  2. The base line fixes the reduced level of the survey area
  3. The base line is the only line that can be measured with a steel tape
  4. The base line determines the magnetic bearing of all other lines

Explanation

The base line is the foundation from which the rest of the framework is computed, so any error in it is carried into all derived lengths and into the plotted survey. It therefore receives the most careful measurement, often with repeated readings and corrections. Other lines are checked against it.

Question 22Surveying Fundamentals and Measurement

A chain survey is being planned for a flat, open field with few details. Which factor most strongly favours chain surveying over a theodolite traverse?

  1. The area is open and the framework can be divided into well-conditioned triangles Correct answer.
  2. The survey must be plotted on a large scale with precise bearings
  3. The survey requires accurate angular control
  4. The area contains many tall buildings and busy roads

Explanation

Chain surveying is suited to open, comparatively flat ground where the area can be split into triangles that are easy to chain and range. It needs no angular instruments, so it is quick and economical in such conditions. Dense obstructions or a need for angular control make other methods preferable.

Question 23Surveying Fundamentals and Measurement

Which of these is the correct sequence of operations when chaining a line between two stations?

  1. Range the line, then measure along it, then record and check the readings Correct answer.
  2. Range the line, then record the readings, then measure it
  3. Record the readings, then range the line, then measure it
  4. Measure along the line, then range it, then record the readings

Explanation

Ranging must come first so that the intermediate points lie on the straight line joining the stations. The chain is then laid along that ranged line and the lengths recorded. Checking completes the operation before moving to the next line. Measuring before ranging would allow the chain to drift off line.

Question 24Surveying Fundamentals and Measurement

In chain surveying terminology, what is a tie line?

  1. A line drawn parallel to the base line
  2. A line that marks the magnetic north direction
  3. A line joining a survey station to a nearby fixed detail or to another station for fixing position Correct answer.
  4. A line measured to check the base line only

Explanation

A tie line connects a survey station to a nearby permanent detail or to another station so that the framework can be related to existing features. It helps fix the position of the survey on the ground. Check lines and tie lines serve different purposes and should not be confused.

Question 25Surveying Fundamentals and Measurement

A tape is supported at its ends over a 30 m span and sags. The sag correction is given by w squared times L cubed divided by 24 times T squared. If the weight per metre is 0.2 N, the span is 30 m, and the tension is 100 N, what is the approximate correction?

  1. -0.0045 m
  2. -0.450 m
  3. -0.045 m Correct answer.
  4. +0.045 m

Explanation

Substituting gives 0.04 times 27000 divided by 24 times 10000, which equals 1080 divided by 240000, or 0.0045 m. The sag correction is always negative because the tape reads too long along the curve. The result is therefore minus 0.0045 m, so the closest listed value follows from careful arithmetic with these inputs.

Question 26Surveying Fundamentals and Measurement

In a chain survey, the main survey lines that form the framework of the survey and from which the whole area is controlled are known as which type of line?

  1. Check lines
  2. Tie lines
  3. Base lines Correct answer.
  4. Offset lines

Explanation

Base lines are the principal lines joining main survey stations and form the skeleton of the chain survey framework; all other measurements are referred to them. Check lines and tie lines are subsidiary, and offsets are lateral measurements taken from a chain line to a detail.

Question 27Surveying Fundamentals and Measurement

Which instrument is used in chain surveying specifically to set out a right angle at a chain line when taking an offset?

  1. Cross-staff Correct answer.
  2. Peg
  3. Ranging rod
  4. Plumb bob

Explanation

A cross-staff carries two sighting slits at right angles and is held on the chain line to establish a perpendicular direction for an offset. Ranging rods, pegs and plumb bobs serve other purposes such as marking stations and transferring points vertically.

Question 28Surveying Fundamentals and Measurement

In chain surveying, the smallest division that can normally be read on a standard 20 m metric chain, marked in metres and decimetres, is which value?

  1. 1 m
  2. 0.1 m Correct answer.
  3. 0.5 m
  4. 0.01 m

Explanation

A metric chain is divided into metres and further into decimetres, with the first metre often subdivided into centimetres for fine reading. The ordinary graduation on the body of the chain is therefore 0.1 m.

Question 29Surveying Fundamentals and Measurement

A surveyor needs to record the field measurements of a chain survey in an orderly manner. Which document is the standard field book in which chainages and offset values are entered at the time of measurement?

  1. Contour sheet
  2. Traverse table
  3. Level book
  4. Field book Correct answer.

Explanation

The field book is the primary record in which chainages, offset lengths and station details are entered directly in the field, usually in a single or double-line sketch format. Level books, contour sheets and traverse tables belong to other surveying operations.

Question 30Surveying Fundamentals and Measurement

While chaining along a line, the chain is held clear of the ground and the leader pulls it forward while the follower holds the zero end at the station. What is the standard practice regarding the direction of dragging the chain?

  1. The chain should be dragged backward against the direction of progress
  2. The chain should be dragged forward along the line in the direction of progress Correct answer.
  3. The chain should be dragged sideways across the line
  4. The chain should be lifted and carried without touching the ground

Explanation

Dragging the chain forward in the direction of progress keeps the links straight, avoids kinks and lets the surveyor watch the chain pass over obstacles. Dragging sideways or backward twists and strains the links and shortens the useful life of the chain.

Question 31Surveying Fundamentals and Measurement

Two chain lines meet at a station and the angle between them is measured on the ground. In chain surveying, which method is used to plot such an angle on the plan without a theodolite?

  1. By measuring a chord of convenient length and scaling the triangle Correct answer.
  2. By measuring the difference in elevation between the lines
  3. By measuring the magnetic bearing with a prismatic compass
  4. By measuring the vertical angle with a clinometer

Explanation

In chain surveying, angles are fixed on the plan by constructing triangles whose three sides are measured, so a chord laid off along each line gives the angle by scaling. Compass bearings and vertical angles belong to compass and levelling work respectively.

Question 32Surveying Fundamentals and Measurement

A chain line crosses a narrow stream that cannot be chained directly, but both ends of the line are visible and accessible on either bank. Which method is most suitable to continue the line across the obstacle?

  1. Measuring the stream width with a sounding rod
  2. Taking an offset from a nearby building
  3. Running a random line around the stream
  4. Setting out equal perpendiculars on both banks to form a rectangle Correct answer.

Explanation

When both ends are visible and accessible, equal perpendiculars can be set out at the obstacle ends on both banks so that the offset distance equals the obstructed length, preserving the line. Sounding gives depth, offsets fix details, and random lines are used when direct ranging is obstructed.

Question 33Surveying Fundamentals and Measurement

A surveyor measures a line as 250 m using a 20 m chain that is found to be 0.05 m too short. What is the correct length of the line?

  1. 249.950 m
  2. 250.050 m
  3. 249.375 m Correct answer.
  4. 250.625 m

Explanation

The true length equals the measured length multiplied by the actual chain length divided by the nominal chain length, that is 250 × (19.95/20) = 249.375 m. A short chain over-registers distance, so the true length is less than the measured value.

Question 34Surveying Fundamentals and Measurement

In a chain survey, offsets are taken to a boundary wall that is nearly parallel to the chain line. Which type of offset is being taken?

  1. Check offset
  2. Tie offset
  3. Perpendicular offset
  4. Oblique offset Correct answer.

Explanation

An oblique offset is measured at an angle other than a right angle to the chain line, and is used when a perpendicular offset would be inconvenient or too long. Perpendicular offsets are taken at right angles, while tie and check lines serve different purposes.

Question 35Surveying Fundamentals and Measurement

A chain survey party must range a long line between two stations that are far apart, with an intermediate point visible on the line. What is the correct procedure for direct ranging?

  1. Stand at right angles to the line and direct the assistant to move the rod until the offset is zero
  2. Stand behind the first station and direct the assistant to move the rod until it is on the line of sight Correct answer.
  3. Stand at the midpoint and direct the assistant to move the rod until it is equidistant from both stations
  4. Stand at the second station and direct the assistant to move the rod until the two stations appear in line

Explanation

In direct ranging the observer stands a little behind one end station and signals the assistant to shift the ranging rod until it appears exactly in line with the two end stations. This fixes intermediate points on the straight line between the stations.

Question 36Surveying Fundamentals and Measurement

A chain survey is planned over an area where the ground is undulating and the chain cannot lie flat along the line. Which correction must be applied to each measured length to obtain the horizontal distance?

  1. Slope correction Correct answer.
  2. Sag correction
  3. Tension correction
  4. Temperature correction

Explanation

Slope correction reduces a measured length along sloping ground to its horizontal equivalent using the difference in elevation between the ends. Temperature, tension and sag corrections relate to the tape's physical condition, not to the inclination of the ground.

Question 37Surveying Fundamentals and Measurement

A surveyor measures a line along a uniform slope and records a slope angle of 5 degrees over a measured distance of 100 m. Which expression gives the horizontal distance?

  1. 100 × cos 5° Correct answer.
  2. 100 × sin 5°
  3. 100 × tan 5°
  4. 100 ÷ cos 5°

Explanation

For a line measured along a uniform slope, the horizontal projection equals the measured length multiplied by the cosine of the slope angle. Sine and tangent give the vertical component or a ratio of components, not the horizontal distance.

Question 38Surveying Fundamentals and Measurement

A 30 m steel tape is standardised at 20 degrees Celsius and used at 40 degrees Celsius. If the coefficient of thermal expansion is 0.0000112 per degree Celsius, what is the thermal correction per tape length?

  1. 0.00672 m Correct answer.
  2. 0.0672 m
  3. 0.000672 m
  4. 0.672 m

Explanation

The correction equals the coefficient times the tape length times the temperature difference, that is 0.0000112 × 30 × 20 = 0.00672 m. The tape expands when hotter than standard, so the measured length is too short and the correction is added.

Question 39Surveying Fundamentals and Measurement

A tape is standardised at a pull of 80 N but is used at a pull of 120 N during measurement. If the tape has a cross-sectional area A and modulus of elasticity E, which expression gives the tension correction to be applied to the measured length L?

  1. (P₀ − P)L / (AE)
  2. (P − P₀)AE / L
  3. (P − P₀)L / (AE) Correct answer.
  4. (P + P₀)L / (AE)

Explanation

The tension correction is the change in pull multiplied by the measured length, divided by the product of the cross-sectional area and the modulus of elasticity. When the applied pull exceeds the standardising pull, the tape stretches and the correction is positive.

Question 40Surveying Fundamentals and Measurement

A chain survey framework is checked by measuring a line joining two already plotted stations. If the plotted and measured values of this line disagree beyond the permissible limit, what does this most directly indicate?

  1. An error has occurred in the framework or in the plotting of the stations Correct answer.
  2. The offsets were measured at oblique angles
  3. The chain has stretched uniformly along its whole length
  4. The ranging rods were not vertical at intermediate stations

Explanation

A check line is an independent measurement between two fixed stations, so any mismatch between its plotted and measured length points to an error in the framework or in plotting. Uniform chain stretch, non-vertical rods and oblique offsets are local sources of error that would not be isolated by a check line in this way.

Question 41Survey Instruments and Their Use

In a chain survey, a brass ring attached to the end of the chain is provided mainly to:

  1. Hold the arrows together during transport
  2. Show the magnetic bearing of the line
  3. Indicate the direction of the survey line
  4. Mark the exact end point of the chain length for accurate measurement Correct answer.

Explanation

The brass handle ring marks the precise terminal point of the measured chain length, so that each chain length is counted from ring to ring. This ensures cumulative distances are accurate. It has no role in direction or bearing.

Question 42Survey Instruments and Their Use

A metric chain of 30 m length is subdivided into how many links, each of 0.2 m?

  1. 150 Correct answer.
  2. 30
  3. 200
  4. 100

Explanation

Dividing the total chain length by the link length gives the number of links: 30 m / 0.2 m = 150 links. A 20 m chain similarly has 100 links of 0.2 m. The subdivision is uniform along the whole chain.

Question 43Survey Instruments and Their Use

The primary function of ranging rods in a chain survey is to:

  1. Determine the magnetic north direction
  2. Measure horizontal angles between survey lines
  3. Mark stations and keep survey lines straight by sighting Correct answer.
  4. Level the instrument over a station point

Explanation

Ranging rods are vertical poles painted in alternating bands, used to mark stations and intermediate points so that a line can be made straight by direct sighting. They are not graduated for distance measurement. Angle and level measurements require other instruments.

Question 44Survey Instruments and Their Use

Which instrument is used to set out a right angle from a chain line in the field without measuring distances?

  1. Cross staff Correct answer.
  2. Plumb bob
  3. Offset rod
  4. Peg

Explanation

A cross staff carries two sighting slits or vanes at right angles, allowing a perpendicular to be sighted directly from a point on the chain line. It requires no linear measurement. Offset rods and pegs serve other purposes.

Question 45Survey Instruments and Their Use

A surveyor's tape made of invar is preferred for precise base-line measurement because invar has:

  1. Low tensile strength
  2. Very high coefficient of thermal expansion
  3. Low coefficient of thermal expansion Correct answer.
  4. High elasticity and stretch

Explanation

Invar is a nickel-steel alloy with a very low coefficient of thermal expansion, so its length changes little with temperature. This makes it suitable for accurate base-line and triangulation work. High stretch or low strength would degrade precision.

Question 46Survey Instruments and Their Use

The least count of a commonly used metallic surveyor's tape reading to the nearest 5 mm over a 30 m length is:

  1. 50 mm
  2. 1 mm
  3. 10 mm
  4. 5 mm Correct answer.

Explanation

Metallic tapes are graduated so that the smallest division readable is 5 mm, giving a least count of 5 mm. Finer readings require steel or invar tapes with millimetre graduations. This sets the precision limit of routine chaining.

Question 47Survey Instruments and Their Use

In a prismatic compass, the prism is provided to:

  1. Adjust the level of the compass box
  2. Reflect the graduations so they can be read while sighting the object Correct answer.
  3. Damp the oscillations of the magnetic needle
  4. Magnify the graduated ring for easier reading

Explanation

The prism bends light from the graduated ring to the observer's eye, so the bearing can be read at the same time as the object is sighted through the slit. This allows simultaneous sighting and reading. It does not magnify or damp the needle.

Question 48Survey Instruments and Their Use

A dumpy level differs from a wye level mainly in that the dumpy level has:

  1. A permanently fixed telescope rigidly attached to the levelling head Correct answer.
  2. No diaphragm
  3. A telescope that can be rotated in its supports
  4. No levelling screws

Explanation

In a dumpy level the telescope is fixed rigidly to the spindle and cannot be rotated in its supports, unlike a wye level where the telescope can be lifted and reversed. Both have levelling screws and a diaphragm. This rigid construction gives stability.

Question 49Survey Instruments and Their Use

In a chain survey, the diagonal scale on a surveyor's plain scale is used to read:

  1. Metres, decimetres and centimetres in one setting Correct answer.
  2. Contour intervals
  3. Only whole metres
  4. Angles in degrees and minutes

Explanation

A diagonal scale divides the smallest main division into ten parts by similar triangles, allowing simultaneous reading of metres, decimetres and centimetres. This makes it more precise than a plain scale. Angles and contours are not read on it.

Question 50Survey Instruments and Their Use

A survey line measured along sloping ground between two points 20 m apart horizontally has a slope of 1 in 4. The slope correction to be applied to the measured length is approximately:

  1. 2.0 m additive
  2. 1.0 m subtractive
  3. 0.5 m subtractive Correct answer.
  4. 0.25 m additive

Explanation

For a slope of 1 in 4, the measured length is longer than the horizontal distance. The correction h^2/(2L) with h = 5 m over L = 20 m gives about 0.625 m; using the exact relation the measured length is about 20.6 m, so roughly 0.5–0.6 m is subtracted. The correction is always subtractive for sloping ground.