Sri Lanka Licensed Surveyor Exam key terms

A survey that defines, marks and records the boundaries and area of land parcels for land registration, taxation and land management. It produces plans and descriptions that tie each parcel to its legal owner or tenure holder.

A defined area of land with legally recognised boundaries held under one ownership or tenure. It is the basic unit recorded in a cadastral system and is identified by a unique number or lot designation.

In Sri Lankan cadastral practice, the draft survey plan prepared by a licensed surveyor after field measurement, showing lot boundaries, marks and areas. It is submitted for official scrutiny before the final plan is approved.

A durable physical mark such as a concrete post, iron pin or rock mark placed at a parcel corner to evidence the boundary on the ground. Its position and description are recorded in the survey plan.

Acquisition of title to land through long, open, continuous possession without the owner's permission. Sri Lankan law sets a limitation period after which the former owner may no longer recover the land.

Physical occupation, construction or cultivation that extends beyond a legally defined boundary onto neighbouring land, a road or a reservation. Surveyors detect it by comparing occupation on the ground with registered parcel limits.

The Sri Lankan statute that governs land survey, registration and licensing of surveyors, and the powers of the Surveyor General. It provides the legal foundation for cadastral plans used in land dealings.

The older geodetic datum of Sri Lanka, computed on the Everest 1830 ellipsoid from an origin at Kandawala. Many historical cadastral, topographic and engineering surveys are still referenced to it.

Sri Lanka Datum 1999, the modern geocentric datum adopted for national mapping and GNSS-based surveying in Sri Lanka. It is realised by a network of GPS-derived control points and agrees closely with WGS84.

An oblate reference ellipsoid defined in 1830 for the Survey of India. Its semi-major axis and flattening underpin the Kandawala datum and therefore much of Sri Lanka's historical mapping and grid coordinates.

The separation at a point between the geoid, an equipotential surface approximating mean sea level, and a chosen reference ellipsoid. It converts GNSS ellipsoidal heights into orthometric heights used in levelling and engineering.

A conformal map projection in which a cylinder touches the ellipsoid along a chosen meridian and is wrapped around it. Sri Lanka's national grid is based on it, giving low distortion over the island's north-south extent.

The angle at a point between grid north and true, or geodetic, north, arising from the curvature of the map projection. Surveyors apply it when converting bearings between grid and geographic references.

A survey method in which successive connected lines between stations are measured for length and direction to compute coordinates for each point. It is widely used for control, boundary and route surveys.

The difference between a measured survey quantity and its known or geometrically required value, such as the gap in a closed traverse or loop of levels. It reveals measurement error and must be assessed before adjustment.

A traverse adjustment technique that spreads the closing error over the legs in proportion to their lengths. It is simple and suits surveys where angular and linear errors are of comparable, random character.

A statistical method that estimates unknown coordinates or parameters by minimising the weighted sum of squared residuals. It yields the most probable solution together with a rigorous assessment of precision and reliability.

The variance of unit weight estimated from the residuals after a least-squares adjustment. A value close to one suggests the assumed observation weights and the stochastic model are realistic.

The vector between two satellite receivers computed from simultaneous carrier-phase observations, expressed in a geocentric reference frame. Processed baselines provide the precise relative positions used to establish survey control.

A GNSS technique in which carrier-phase corrections are sent from a base station or network to a rover, giving centimetre-level coordinates in the field. It is common in cadastral surveying, setting out and detail surveys.

A Continuously Operating Reference Station: a permanently installed GNSS receiver at a known point that streams correction and observation data to users. Networks of these stations maintain and densify the national geodetic frame.

A numerical factor describing how satellite geometry degrades the accuracy of a GNSS position fix. Low values indicate good geometry and reliable positions, while high values warn that accuracy may be poor.

A stable, precisely levelled point of known reduced level that serves as reference for vertical control. Bench marks transfer heights to construction sites and are used to check and adjust levelling networks.

The process of marking on the ground the position, level and alignment of designed works, using coordinates, offsets or bearings from established control. Permissible tolerances depend on the type and purpose of the structure.

A method in which an instrument's coordinates and orientation are derived by observing several known control points from a freely chosen setup position. It saves time where occupying a control point is difficult or unsafe.

A line on a plan joining points of equal height above a stated datum, used to depict terrain shape. Close spacing indicates steep ground, wide spacing indicates gentle slopes, and contours never cross one another.

An aerial or satellite image geometrically rectified to remove relief displacement and sensor tilt, giving it map-like properties. Distances, angles and areas can be measured on it within stated accuracy.

A digital representation of terrain height at sampled or regularly spaced points, stored as a grid or triangulated surface. It supports contouring, slope analysis, drainage modelling and earthwork volume computation.

Light Detection and Ranging: a system that measures ranges by timing laser pulses reflected from ground, vegetation and structures, producing dense point clouds. It supports detailed terrain models, corridor mapping and canopy studies.

A point whose coordinates are known from field survey and can be clearly identified in imagery or point clouds. Such points georeference, verify and control photogrammetric and remote-sensing products.

A photogrammetric computation that solves camera parameters, image orientations and object point coordinates simultaneously from overlapping images using tie points and control. It produces accurate, internally consistent mapping coordinates.

A system in which the state keeps a register that records ownership and interests in each parcel, so that the register itself is evidence of title. It differs from systems that merely record the deeds of transaction.

A computerised system holding spatial and textual land records, such as parcels, owners, tenure and survey data, linked to a cadastral map base. It supports land administration, planning, valuation and taxation.

A system that registers the instruments of transfer and other dealings instead of the title itself. Ownership is proved by tracing an unbroken chain of deeds, so boundary and interest certainty may be weaker.

The statutory body in Sri Lanka that registers and licenses land surveyors, sets standards of practice and handles discipline. Unlicensed practice is unlawful for surveys that must be accepted by the state.

A surveyor's failure to exercise the skill and care reasonably expected of the profession, resulting in loss to a client or third party. It may give rise to civil liability, insurance claims and disciplinary proceedings.

The low-water reference level from which depths printed on nautical charts and predicted tide heights are measured. It is selected so that actual water level seldom falls below the charted depths.

A hydrographic method that measures water depth by timing an acoustic pulse travelling from a transducer to the seabed and back. Single-beam and multibeam systems are used for navigation charts and dredging surveys.