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Sri Lanka Licensed Surveyor Exam practice questions

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Question 1Cadastral Surveying and Land Parcel Definition

Under Sri Lankan cadastral practice, what is the primary purpose of a cadastral survey?

  1. To delineate forest and wildlife reserve boundaries
  2. To define parcel boundaries and create the spatial record used for land registration Correct answer.
  3. To estimate the market value of each land parcel for taxation
  4. To map general topography for road and drainage design

Explanation

A cadastral survey establishes parcel geometry, boundary marks and parcel identifiers so that rights in land can be registered. Topographic mapping, valuation and reserve demarcation are separate functions and do not by themselves create a cadastral parcel record.

Question 2Cadastral Surveying and Land Parcel Definition

Which Sri Lankan statute provides the framework for carrying out cadastral surveys and preparing cadastral maps?

  1. Cadastral Survey Act No. 24 of 2004 Correct answer.
  2. Town and Country Planning Ordinance No. 13 of 1946
  3. Land Development Ordinance No. 19 of 1935
  4. Registration of Title Act No. 21 of 1998

Explanation

The Cadastral Survey Act No. 24 of 2004 provides the statutory framework for cadastral surveys and cadastral map preparation in Sri Lanka. The other statutes govern land development, title registration and planning control rather than the conduct of cadastral surveys.

Question 3Cadastral Surveying and Land Parcel Definition

On a cadastral map, what is the basic land unit bounded by parcel boundaries and identified by a unique number?

  1. A bench mark
  2. A grid line
  3. A contour interval
  4. A land parcel Correct answer.

Explanation

A land parcel is the basic cadastral unit, bounded by parcel boundaries and identified by a unique parcel number on the cadastral map. Contours, bench marks and grid lines are survey reference features, not land units.

Question 4Cadastral Surveying and Land Parcel Definition

A licensed surveyor finds an original corner monument whose position differs from the distance written in the deed. What is the correct cadastral principle to apply?

  1. Adopt the occupied fence line regardless of the monument
  2. Reject the monument because the deed distance is conclusive
  3. Move the monument to the deed distance without notice
  4. Rely on the original monument and check the survey record Correct answer.

Explanation

Original boundary marks are generally stronger evidence of the boundary as originally established than distances written in a deed. The surveyor should check the prior plan, field notes and adjoining parcels before deciding whether the mark has been disturbed.

Question 5Cadastral Surveying and Land Parcel Definition

A cadastral parcel has corner coordinates in metres (100,100), (200,100), (200,200) and (100,200). Using the coordinate method, what is its area?

  1. 0.5 hectare
  2. 2.0 hectares
  3. 1.0 hectare Correct answer.
  4. 10.0 hectares

Explanation

The four corners form a 100 m by 100 m square, giving an area of 10,000 square metres. Since one hectare is 10,000 square metres, the parcel area is 1.0 hectare.

Question 6Cadastral Surveying and Land Parcel Definition

Why is a unique parcel identifier important in a Sri Lankan cadastral system?

  1. It links the spatial parcel to the registry record and ownership information Correct answer.
  2. It defines the topographic contour of the parcel
  3. It removes the need to maintain boundary marks in the field
  4. It sets the market value of the parcel for compensation

Explanation

A unique parcel identifier allows the spatial parcel on the cadastral map to be matched to the registry record, owner and rights. Without that link, spatial and textual land records cannot be reliably integrated.

Question 7Cadastral Surveying and Land Parcel Definition

When preparing a cadastral survey for a land parcel, which source should a licensed surveyor check first to confirm the registered extent and boundary description?

  1. An agricultural census report
  2. The latest tourist map of the area
  3. The title deed and any prior survey plan Correct answer.
  4. A neighbouring owner's verbal statement

Explanation

The title deed and any prior survey plan are the primary records of the registered extent and boundary description. They should be checked before field evidence is interpreted or a new plan is prepared.

Question 8Cadastral Surveying and Land Parcel Definition

During a cadastral survey, a concrete boundary mark is found displaced, while the adjacent original marks are intact. What is the proper professional response?

  1. Re-establish the corner by proportioning between the nearest intact marks and record it as original
  2. Investigate the displacement, use original records and adjacent marks, and report the reinstatement Correct answer.
  3. Use the displaced mark as the corner because physical evidence always prevails
  4. Ignore the mark and adopt the current fence line as the boundary

Explanation

A displaced mark is not reliable evidence of the original corner, and proportioning is only appropriate in defined lost-corner situations after analysis. The surveyor should examine the original plan, field notes and adjacent marks, then document and report how the corner was reinstated.

Question 9Cadastral Surveying and Land Parcel Definition

What distinguishes a fixed boundary from a general boundary in cadastral surveying?

  1. Both boundary types are treated as identical because every cadastral parcel has a fixed boundary
  2. A fixed boundary is monumented and coordinated, while a general boundary lacks precise coordinates Correct answer.
  3. A fixed boundary may be shifted by the owner at will, while a general boundary is permanently fixed by law
  4. A general boundary is always recorded with coordinates, while a fixed boundary depends on oral evidence

Explanation

A fixed boundary is surveyed and monumented so that its position is mathematically defined. A general boundary is shown by reference to a physical feature such as a fence or hedge and is not normally given a precise coordinate definition.

Question 10Cadastral Surveying and Land Parcel Definition

A registered land parcel is to be subdivided into three new lots. Before the new lots can be entered in the land register, what is normally required?

  1. A verbal agreement among the neighbours witnessed by the village officer
  2. A valuation report prepared for property taxation
  3. An approved cadastral or subdivision survey plan defining each new lot Correct answer.
  4. A topographic map of the entire district

Explanation

Subdivision requires a surveyed plan that defines the new parcel boundaries, areas and access so that each lot can be identified in the register. A verbal agreement or a valuation report does not create registrable parcel geometry.

Question 11Cadastral Surveying and Land Parcel Definition

In Sri Lankan cadastral records, land areas are still commonly expressed in perches. One perch is approximately equal to which area in square metres?

  1. 25.29 m² Correct answer.
  2. 40.47 m²
  3. 10.12 m²
  4. 101.17 m²

Explanation

One acre equals 40 perches and 4 046.86 m², so a perch is 4 046.86 ÷ 40 ≈ 25.29 m². This factor is the one used when areas recorded in perches on cadastral documents are converted to metric units for mapping and registration. Getting the factor wrong changes every computed parcel area and every area discrepancy check on the plan.

Question 12Cadastral Surveying and Land Parcel Definition

The Bim Saviya programme in Sri Lanka is best described as:

  1. a programme for resurveying only State forest boundaries
  2. a licensing scheme for private surveyors practising cadastral surveys
  3. a scheme for converting perches into hectares in land registry records
  4. a national programme for adjudicating land parcels and issuing registered title certificates Correct answer.

Explanation

Bim Saviya is the national land title registration programme, under which parcels are adjudicated, surveyed and then entered in the title register with certificates issued to landowners. The cadastral survey is one component of that wider adjudication and registration process, not the programme itself. Understanding this helps a surveyor see where the survey plan fits in the legal chain.

Question 13Cadastral Surveying and Land Parcel Definition

A deed records a parcel of 3 acres and 10 perches. Using 1 acre = 40 perches and 1 perch = 25.29 m², what is the parcel area in hectares?

  1. 1.300 ha
  2. 0.329 ha Correct answer.
  3. 0.132 ha
  4. 3.288 ha

Explanation

Three acres is 120 perches, and adding the 10 perches gives 130 perches. Multiplying 130 by 25.29 m² gives about 3 287.7 m², which is 0.329 ha because one hectare is 10 000 m². The metric area must be derived from the total perch count, not from the acre figure alone.

Question 14Cadastral Surveying and Land Parcel Definition

Cadastral surveys in Sri Lanka are georeferenced to which current national horizontal datum?

  1. Everest 1830
  2. Kandawala datum
  3. WGS 84
  4. Sri Lanka Datum 1999 (SLD99) Correct answer.

Explanation

SLD99 is the national geodetic datum established in 1999 and used as the reference frame for surveying and mapping in Sri Lanka. Cadastral control is connected to it so that parcels across the country sit on one consistent coordinate system. Using a superseded or purely global frame would create inconsistencies with the national mapping base.

Question 15Cadastral Surveying and Land Parcel Definition

During re-establishment, a cadastral corner on a straight boundary line is found to be lost. The two nearest original marks on that line are intact, but the measured distance between them is slightly greater than the distance shown on the approved survey. How should the lost corner be replaced?

  1. At the midpoint of the measured line
  2. At the recorded distance from the nearer original mark, ignoring the measured length
  3. At a point on the line that divides the measured distance in the same proportion as the recorded distances from the lost corner to the two original marks Correct answer.
  4. At the intersection of the recorded bearings of the two adjoining boundary lines, regardless of the original marks

Explanation

Where a corner is lost but original marks survive on the same line, single proportionate measurement is used: the measured distance between the surviving marks is divided in the ratio of the recorded distances. This preserves the original relationship between the corner and the controlling monuments while absorbing the small difference between record and measurement. Placing the corner at a raw record distance would distort that relationship.

Question 16Cadastral Surveying and Land Parcel Definition

A closed traverse around a parcel closes with a misclosure that is within the allowable limit for the survey standard being applied. What is the correct treatment before coordinates are computed and the plan is drawn?

  1. Ignore the misclosure because it is within the allowable limit
  2. Force the last traverse line to close exactly, leaving the other lines unadjusted
  3. Adjust the traverse by a recognised method such as Bowditch so that the closure error is distributed consistently Correct answer.
  4. Increase the parcel area to absorb the area equivalent of the misclosure

Explanation

A misclosure within tolerance still has to be distributed, normally by a recognised adjustment such as the Bowditch (compass) rule, so that the computed coordinates form a consistent closed figure. Ignoring it leaves the traverse mathematically open and inconsistent with the plotted boundary. Confining the whole error to the final line produces a distorted parcel shape.

Question 17Cadastral Surveying and Land Parcel Definition

In the first-registration (title settlement) process in Sri Lanka, which officer investigates and determines claims to parcels before title is registered?

  1. The adjudication officer Correct answer.
  2. The licensed surveyor alone
  3. The local authority valuer
  4. The land registry clerk

Explanation

Adjudication is a distinct statutory function in which an adjudication officer investigates ownership claims, hears evidence and determines the rights to be recorded for each parcel. The licensed surveyor supplies the boundary survey and cadastral map that support that determination but does not decide ownership. Keeping the two roles separate is fundamental to the integrity of first registration.

Question 18Cadastral Surveying and Land Parcel Definition

A parcel fronts a public road, and an approved road reservation plan shows the limit of the road reservation. Which line should the licensed surveyor adopt as the parcel's road-side boundary?

  1. The edge of the bitumen surface
  2. The road reservation boundary shown on the approved plan Correct answer.
  3. The centreline of the carriageway
  4. The line of the existing fence, whatever its position

Explanation

The road reservation is held for the road authority or the State, so the private parcel ends at the reservation limit recorded on the approved plan. The carriageway centreline and the sealed edge are construction features that can shift with widening or resurfacing and do not define ownership. An occupation fence that encroaches into or out of the reservation cannot override the approved reservation line.

Question 19Cadastral Surveying and Land Parcel Definition

Two approved survey plans for adjoining parcels show boundaries that overlap by 0.4 m along a shared line. What is the most appropriate professional response by the licensed surveyor preparing a new survey of one of the parcels?

  1. Adopt the boundary shown on the more recently approved plan
  2. Investigate the original marks and records of both parcels, and refer the discrepancy to the Surveyor General's office for resolution before issuing the new plan Correct answer.
  3. Adopt the mean line between the two approved boundaries
  4. Adopt the line that gives the larger area to the parcel being surveyed

Explanation

An overlap between approved plans is a conflict in the cadastral record, not something the individual surveyor may settle by splitting the difference or choosing a favourite line. The proper course is to examine the original monuments and field evidence for both parcels and escalate the discrepancy through the Surveyor General's office so that the record is corrected officially. Issuing a third inconsistent plan would multiply the problem.

Question 20Cadastral Surveying and Land Parcel Definition

A straight parcel boundary runs 141.42 m from corner P at (1000.00, 2000.00) on a bearing of 225°. Taking northings first and eastings second, what are the coordinates of the other corner Q?

  1. (900.00, 1900.00) Correct answer.
  2. (900.00, 2100.00)
  3. (1100.00, 1900.00)
  4. (1100.00, 2100.00)

Explanation

A bearing of 225° lies in the south-west quadrant, so both the northing and the easting decrease. The changes are 141.42 × cos 225° = −100.00 m in northing and 141.42 × sin 225° = −100.00 m in easting. Applying these to P gives Q at (900.00, 1900.00).

Question 21Cadastral Surveying and Land Parcel Definition

In Sri Lankan cadastral practice, which term refers to an area of land occupied and managed as a single unit that may consist of more than one cadastral parcel?

  1. A map sheet
  2. A block
  3. A lot
  4. A holding Correct answer.

Explanation

A holding is the land occupied and managed as one operational unit, while a cadastral parcel is the basic mapped and numbered unit. Because one occupier may use several adjoining parcels, the holding can contain more than one parcel.

Question 22Cadastral Surveying and Land Parcel Definition

What is a cadastral block in Sri Lankan parcel numbering?

  1. A group of adjoining parcels bounded by roads or streams for reference numbering Correct answer.
  2. A single parcel that has been subdivided into building lots
  3. A map sheet showing only survey control points
  4. The total land area owned by one family in a village

Explanation

A cadastral block groups contiguous parcels within visible or agreed limits, such as roads or streams, and provides a reference framework for parcel numbering. It is not itself a parcel or an ownership unit.

Question 23Cadastral Surveying and Land Parcel Definition

What does a mutation in the cadastral record normally record?

  1. The original survey of a village before first registration
  2. The appointment of a licensed surveyor to a district
  3. The conversion of perches to square metres
  4. A change to parcel boundaries or identity after subdivision or amalgamation Correct answer.

Explanation

A mutation records a later change to the cadastral fabric, such as a subdivision, amalgamation, boundary correction, or renumbering. It keeps the parcel record current after the original survey.

Question 24Cadastral Surveying and Land Parcel Definition

In Sri Lanka, what is the principal function of the Surveyor General in relation to cadastral survey plans prepared by licensed surveyors?

  1. Determining ownership disputes between private claimants in the courts
  2. Collecting land revenue from registered parcels for local authorities
  3. Issuing title certificates to individual landowners after registration is completed
  4. Examining and approving survey plans for compliance with survey standards Correct answer.

Explanation

The Surveyor General is the professional head of the Survey Department and approves cadastral survey plans against prescribed standards before they are accepted into the cadastral record. Title registration and dispute adjudication are handled through the land registration and settlement processes, not by plan approval.

Question 25Cadastral Surveying and Land Parcel Definition

During first registration under a cadastral settlement programme, why is the preliminary survey plan made available for public inspection?

  1. To invite private surveyors to tender for the survey contract
  2. To let landowners and adjoining claimants check boundaries and object before final determination Correct answer.
  3. To publish the names of surveyors who performed the field work
  4. To calculate the market value of each parcel for compensation

Explanation

Public inspection gives affected landowners and adjoining claimants an opportunity to see the proposed parcel boundaries and identifiers and to raise objections before the title determination becomes final. It is a safeguard in the first-registration process, not a procurement or valuation step.

Question 26Cadastral Surveying and Land Parcel Definition

When a cadastral boundary is curved, how is it normally represented in a coordinate-based survey plan?

  1. By a separate inset map at a smaller scale
  2. By a single straight chord between the two end corners, ignoring the curve
  3. By points along the curve joined by chords, with arcs or radii where needed Correct answer.
  4. By a note stating that the boundary is natural and cannot be surveyed

Explanation

A curved cadastral boundary is defined by a sequence of surveyed points along the curve, joined by chords, and where appropriate by arc data such as radius and centre. This preserves the boundary geometry in a coordinate-based record.

Question 27Cadastral Surveying and Land Parcel Definition

Which combination of information on a cadastral survey plan most directly supports retracement of a parcel boundary in the field?

  1. The surveyor's licence number and office address
  2. The parcel area and the land revenue assessment
  3. The owner's name and the date of registration
  4. Boundary bearings and distances and references to marks Correct answer.

Explanation

Retracement requires the geometric definition of each boundary line plus the identity and location of the marks that define the corners. Bearings, distances, and monument references allow the surveyor to search for and test the original boundary evidence in the field.

Question 28Cadastral Surveying and Land Parcel Definition

A deed plan states bearings relative to magnetic north at the date of survey, but the current cadastral control is on grid north. What should the licensed surveyor do before using those bearings?

  1. Replace the magnetic bearings with the distances measured from the deed plan
  2. Reduce the magnetic bearings to grid using the declination at the survey date and place Correct answer.
  3. Use the magnetic bearings unchanged because magnetic bearings never change over time
  4. Add 90 degrees to every magnetic bearing to obtain grid bearings for the plan

Explanation

Magnetic north varies with time and location, so a deed bearing referred to magnetic north must be reduced to the current grid using the appropriate declination before it is compared with control coordinates. Adding a fixed angle or ignoring the difference will misplace the boundary.

Question 29Cadastral Surveying and Land Parcel Definition

A parcel has a deed sketch that shows only distances along a road and a stream, with no bearings or coordinates. What is the most defensible cadastral approach?

  1. Refuse to survey because a deed without bearings cannot define a parcel
  2. Survey the road, stream, and occupation on cadastral control, reconstruct the boundary from the best evidence, and record assumptions and discrepancies Correct answer.
  3. Assume the road frontage runs due north and compute the other lines from the distances
  4. Scale the sketch from the stated area and adopt the scaled lines as the boundary

Explanation

A sketch without bearings is incomplete but not necessarily void; the surveyor should tie visible natural features and occupation to control, reconstruct the boundary from the best evidence, and disclose assumptions and conflicts. Scaling a sketch or inventing an orientation creates false precision.

Question 30Cadastral Surveying and Land Parcel Definition

A parcel boundary follows a stream. Over 30 years the stream gradually shifts by erosion and deposition, and no statute or grant fixes the line. In cadastral retracement, how should the boundary generally be treated?

  1. It follows the stream as it shifts gradually under accretion and erosion Correct answer.
  2. It is fixed at the centreline of the stream as it existed on the date of first registration
  3. It remains at the original surveyed line regardless of the stream's movement
  4. It moves only if the shift exceeds one perch in width

Explanation

Where a boundary is a natural feature and no statute or grant fixes the line, gradual and imperceptible movement by accretion or erosion normally carries the boundary with the feature. A sudden avulsion is treated differently, and fixed-line grants override the general rule.

Question 31Geodesy, Geodetic Datums and Coordinate Systems

What is the primary function of a geodetic datum?

  1. To define the reference ellipsoid and coordinate origin Correct answer.
  2. To set contour intervals for terrain models
  3. To record magnetic declination at a survey station
  4. To specify map colours, symbols and legend layout

Explanation

A geodetic datum fixes the reference ellipsoid, its position and orientation, and the coordinate origin so that positions can be expressed consistently on the Earth. Without a datum, latitude, longitude and height have no unique physical meaning.

Question 32Geodesy, Geodetic Datums and Coordinate Systems

Which surface is the geoid?

  1. An equipotential gravity surface near mean sea level Correct answer.
  2. A plane tangent to the ellipsoid at the datum origin
  3. The physical topographic surface of the Earth
  4. The best-fitting reference ellipsoid for a region

Explanation

The geoid is the equipotential surface of the Earth's gravity field that best coincides with mean sea level over the oceans and extends conceptually beneath the continents. Orthometric heights are measured above this surface.

Question 33Geodesy, Geodetic Datums and Coordinate Systems

Most of Sri Lanka lies in which UTM zone?

  1. Zone 42N
  2. Zone 45N
  3. Zone 43N
  4. Zone 44N Correct answer.

Explanation

UTM zones are 6° wide in longitude, and zone 44N spans 78°E to 84°E. Sri Lanka lies approximately between 79.5°E and 81.9°E, so it falls within zone 44N.

Question 34Geodesy, Geodetic Datums and Coordinate Systems

A point has ellipsoidal height h and geoid undulation N, where N is the height of the geoid above the ellipsoid. Which expression gives the orthometric height H?

  1. H = h − N Correct answer.
  2. H = h + N
  3. H = N − h
  4. H = h × N

Explanation

Ellipsoidal height h is measured above the ellipsoid, while orthometric height H is measured above the geoid. Since the geoid lies N above the ellipsoid, h = H + N, so H = h − N.

Question 35Geodesy, Geodetic Datums and Coordinate Systems

Which reference ellipsoid is associated with the Kandawala datum used in Sri Lanka?

  1. GRS80
  2. WGS84
  3. Everest 1830 Correct answer.
  4. Bessel 1841

Explanation

The Kandawala datum, the older local datum used in Sri Lanka, is associated with the Everest 1830 ellipsoid. WGS84 and GRS80 belong to modern geocentric systems, while Bessel 1841 is used in other regions.

Question 36Geodesy, Geodetic Datums and Coordinate Systems

How is the Sri Lanka Datum 1999, SLD99, best described?

  1. A lunar-based reference frame for tide prediction
  2. A geocentric datum compatible with satellite positioning Correct answer.
  3. A vertical datum based on mean sea level
  4. A local datum referenced to the Kandawala origin

Explanation

SLD99 is Sri Lanka's modern geocentric datum, designed to be compatible with satellite-based global reference frames. It replaced the older local Kandawala datum for many national mapping and surveying applications.

Question 37Geodesy, Geodetic Datums and Coordinate Systems

For a Transverse Mercator projection with central scale factor k0, what is the scale factor exactly on the central meridian?

  1. 1/k0
  2. k0 Correct answer.
  3. Zero
  4. sec φ

Explanation

On a Transverse Mercator projection the central meridian is the line of zero distortion before the central scale factor is applied. The scale factor on that meridian therefore equals k0, and it increases with distance from the central meridian.

Question 38Geodesy, Geodetic Datums and Coordinate Systems

Grid convergence is the angle between which two directions?

  1. Ellipsoidal and orthometric height
  2. Grid north and true north Correct answer.
  3. Geodetic and astronomical latitude
  4. Magnetic north and true north

Explanation

Grid convergence is the angle between grid north, the direction of the central meridian on the projection, and true north at the point. It is used to convert between grid bearings and true bearings.

Question 39Geodesy, Geodetic Datums and Coordinate Systems

Which combination of parameters defines a seven-parameter Helmert transformation?

  1. Three translations, three rotations, and one scale factor Correct answer.
  2. Two translations, four rotations, and one scale factor
  3. Seven translations and no rotations
  4. One translation, three rotations, and three scale factors

Explanation

The seven-parameter Helmert transformation consists of three translations, three rotations and one scale factor. It is commonly used to relate coordinates between two geodetic datums or reference frames.

Question 40Geodesy, Geodetic Datums and Coordinate Systems

Which statement correctly distinguishes geodetic latitude from astronomical latitude?

  1. Geodetic latitude uses the ellipsoid normal; astronomical latitude uses the local vertical. Correct answer.
  2. Geodetic latitude is always greater; astronomical latitude is always smaller.
  3. They are identical everywhere because both use the same reference surface.
  4. Geodetic latitude is measured from the geoid; astronomical latitude from the ellipsoid.

Explanation

Geodetic latitude is defined by the direction of the ellipsoid normal at the point, whereas astronomical latitude is defined by the local gravity vertical, or plumb line. The two differ by the deflection of the vertical.

Question 41Geodesy, Geodetic Datums and Coordinate Systems

In a geocentric Cartesian system, which expression gives the X coordinate of a point with geodetic latitude φ, longitude λ and ellipsoidal height h, where N is the radius of curvature in the prime vertical?

  1. (N + h) sin φ cos λ
  2. (N + h) cos φ cos λ Correct answer.
  3. (N(1 − e²) + h) sin φ
  4. (N + h) cos φ sin λ

Explanation

The geocentric Cartesian coordinates of a point on the ellipsoid normal are X = (N + h) cos φ cos λ, Y = (N + h) cos φ sin λ and Z = (N(1 − e²) + h) sin φ. The X coordinate therefore uses the cosine of both latitude and longitude, multiplied by the distance from the ellipsoid along the normal.

Question 42Geodesy, Geodetic Datums and Coordinate Systems

A UTM coordinate for a point exactly on the central meridian has an easting of 500 000 m. What is the purpose of this convention?

  1. It identifies the hemisphere in which the point lies.
  2. It converts grid north to true north at the central meridian.
  3. It keeps easting values positive across the 6° zone. Correct answer.
  4. It removes the need for a northing value in the southern hemisphere.

Explanation

UTM applies a false easting of 500 000 m to the central meridian so that eastings remain positive throughout the zone, avoiding negative coordinates west of the central meridian. The hemisphere is indicated separately, while northing uses a false northing in the southern hemisphere.

Question 43Geodesy, Geodetic Datums and Coordinate Systems

For a reference ellipsoid with semi-major axis a and semi-minor axis b, how is the flattening f defined?

  1. (a − b) / b
  2. b / a
  3. (a − b) / (a + b)
  4. (a − b) / a Correct answer.

Explanation

Flattening is defined as f = (a − b) / a, which expresses the polar flattening as a fraction of the semi-major axis. It is a dimensionless quantity, commonly about 1/298.257 for the GRS80 ellipsoid.

Question 44Geodesy, Geodetic Datums and Coordinate Systems

At geodetic latitude φ, which expression gives the radius of curvature in the prime vertical N for an ellipsoid with semi-major axis a and first eccentricity e?

  1. a / (1 − e² cos²φ)^(1/2)
  2. a / (1 − e² sin²φ)^(1/2) Correct answer.
  3. a(1 − e² sin²φ)^(1/2)
  4. a(1 − e²) / (1 − e² sin²φ)^(3/2)

Explanation

The radius of curvature in the prime vertical is N = a / (1 − e² sin²φ)^(1/2). It is the radius used in the geodetic-to-Cartesian conversion and differs from the meridional radius of curvature.

Question 45Geodesy, Geodetic Datums and Coordinate Systems

Why is an iterative or closed-form algorithm normally required to convert Earth-centred Cartesian coordinates (X, Y, Z) to geodetic latitude, longitude and ellipsoidal height?

  1. The latitude and height appear together in the ellipsoid normal equations, so neither can be solved directly from X, Y and Z alone. Correct answer.
  2. Cartesian coordinates are referred to a sphere, whereas geodetic coordinates use an ellipsoid.
  3. The conversion requires a geoid model to relate gravity to the ellipsoid.
  4. Longitude cannot be obtained from X and Y without a datum transformation.

Explanation

The Cartesian-to-geodetic conversion is implicit because latitude and ellipsoidal height are coupled through the ellipsoid normal equations. Longitude is obtained directly from atan2(Y, X), but latitude and height require iteration or a closed-form solution.

Question 46Geodesy, Geodetic Datums and Coordinate Systems

A Sri Lankan control station has ITRF2014 coordinates at epoch 2010.0 and lies in a region moving about 2 cm per year relative to the ITRF frame. What is the correct treatment when the coordinate is needed at epoch 2025.0?

  1. Apply the station velocity to propagate the coordinate from 2010.0 to 2025.0. Correct answer.
  2. Rotate the coordinate by the grid convergence at the station.
  3. Use the 2010.0 coordinate unchanged because ITRF2014 is a static frame.
  4. Subtract the geoid undulation for 2025.0 from the ellipsoidal height.

Explanation

ITRF realizations are time-dependent, and station coordinates change because of tectonic plate motion and local deformation. A coordinate at a different epoch should be propagated using the station velocity or an appropriate plate-motion model.

Question 47Geodesy, Geodetic Datums and Coordinate Systems

Why must an orthometric correction be applied to precise differential levelling over long distances?

  1. Because equipotential surfaces are not parallel, so observed height differences depend on gravity along the route. Correct answer.
  2. Because atmospheric refraction increases with altitude.
  3. Because the levelling instrument's collimation error changes with distance.
  4. Because the ellipsoid's semi-major axis varies with latitude.

Explanation

Spirit levelling measures height differences between equipotential surfaces, and those surfaces converge toward the poles because gravity varies with latitude. Orthometric correction accounts for this gravity variation so that the result refers consistently to the geoid.

Question 48Geodesy, Geodetic Datums and Coordinate Systems

After instrumental and atmospheric corrections, a measured slope distance between two stations is to be reduced to an ellipsoidal distance. Which sequence is correct?

  1. Reduce the slope distance directly to the ellipsoid using only the station latitudes.
  2. Convert the slope distance to a grid distance and divide by the point scale factor.
  3. Correct for instrument height, reduce to horizontal, then apply the ellipsoid factor. Correct answer.
  4. Apply the ellipsoid factor first, then correct for instrument height, then reduce to the horizontal.

Explanation

The slope distance is first reduced to a horizontal distance at the mean station elevation using instrument and reflector heights. The horizontal distance is then reduced to the ellipsoid using the ellipsoid or sea-level factor based on the height above the ellipsoid.

Question 49Geodesy, Geodetic Datums and Coordinate Systems

In geodesy, how is the meridional component ξ of the deflection of the vertical at a station defined?

  1. Approximately the astronomical latitude minus the geodetic latitude Correct answer.
  2. The difference between orthometric height and ellipsoidal height
  3. The angle between the ellipsoid normal and the geoid normal measured in the prime vertical plane
  4. The geodetic longitude minus the astronomical longitude

Explanation

The meridional component is ξ = Φ − φ, where Φ is astronomical latitude and φ is geodetic latitude; it measures the north-south tilt of the vertical. The prime-vertical component is η = (Λ − λ) cos φ.

Question 50Geodesy, Geodetic Datums and Coordinate Systems

For a Transverse Mercator projection with central scale factor 0.9996, how does the point scale factor behave as the distance from the central meridian increases?

  1. It remains exactly 0.9996 everywhere within the zone.
  2. It decreases continuously with distance from the central meridian.
  3. It increases and eventually exceeds 1.0 at sufficient distance from the central meridian. Correct answer.
  4. It varies only with latitude and is independent of longitude.

Explanation

In the Transverse Mercator projection the scale factor equals k0 on the central meridian and grows approximately with the square of the distance from it. At sufficient distance the scale factor exceeds unity, which is why UTM zones are kept narrow.