SURCON Professional flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Cadastral parcel

A defined land unit with a unique identifier, boundary geometry, and legal or administrative attributes used for land registration and taxation.

Boundary re-establishment hierarchy

When original boundary evidence conflicts, an undisturbed original monument generally ranks above record dimensions, which rank above occupation evidence, subject to governing statute.

Coordinate area formula

The area of a closed polygon is half the absolute sum of cross products of consecutive coordinates: A = 0.5 * |sum(XiYi+1 - Xi+1Yi)|.

Traverse misclosure

Linear misclosure equals the square root of the sum of squared northings and eastings errors; relative precision is traverse perimeter divided by that misclosure.

General boundary

A boundary representation that follows physical features on the ground rather than fixed coordinates; its exact legal line may be determined by occupation or statute.

Fixed boundary

A boundary defined by coordinated geometry and monumented points, enabling mathematical re-establishment with an accuracy class specified by the land registry.

Overlap and gap

In cadastral mapping, parcel overlaps indicate conflicting boundary geometry, while gaps may represent roads, reserves, or survey error requiring investigation before registration.

Geodetic ellipsoid flattening

Flattening is f = (a - b)/a, where a is semi-major and b semi-minor axis; eccentricity squared is e^2 = 2f - f^2.

Geoid undulation relation

Geoid undulation N links ellipsoidal height h and orthometric height H by N = h - H, so orthometric height equals ellipsoidal height minus undulation.

Prime vertical radius

The prime vertical radius is N = a/sqrt(1 - e^2 sin^2(phi)); it is used with ellipsoidal height to convert geodetic latitude, longitude, and height to Cartesian coordinates.

Meridian radius curvature

The meridian radius is M = a(1 - e^2)/(1 - e^2 sin^2(phi))^(3/2); it governs north-south curvature of the ellipsoid at latitude phi.

Seven-parameter Helmert

A Helmert transformation uses three translations, three rotations, and one scale factor to convert coordinates between geodetic datums, often with residual distortion after transformation.

UTM scale factor

Universal Transverse Mercator uses central-meridian scale factor 0.9996; grid distance equals ground distance multiplied by the combined scale factor at that location.

GNSS relative positioning

GNSS relative positioning determines a baseline between receivers by differencing carrier-phase observations, reducing common errors and enabling centimetre-level coordinates after ambiguity resolution.

Photographic scale

For a vertical photograph over flat terrain, scale equals focal length divided by flying height above ground, or photo distance divided by corresponding ground distance.

Relief displacement

On a vertical photograph, relief displacement is d = r*h/H, where r is radial distance, h object height, and H flying height above datum.

Ground sample distance

Ground sample distance equals pixel size multiplied by flying height above ground divided by focal length; it defines the ground footprint of one image pixel.

Orthophoto

An orthophoto is a geometrically corrected image in which relief displacement and camera tilt are removed using a digital elevation model, allowing map-like measurement.

NDVI formula

Normalized Difference Vegetation Index equals near-infrared minus red divided by near-infrared plus red; values range from minus one to plus one.

DSM versus DTM

A digital surface model includes vegetation and built objects, while a digital terrain model represents bare earth; the choice depends on drainage, visibility, or surface analysis.

Map scale fraction

A representative fraction such as 1:50,000 means one map unit represents 50,000 ground units; a larger scale has a smaller denominator and shows more detail.

Conformal projection

A conformal map projection preserves local angles and shape at the expense of area; it is preferred for navigation and large-scale topographic mapping where angular fidelity matters.

Equal-area projection

An equal-area projection preserves the area of mapped regions but distorts shape and angles; it is used for thematic maps comparing density or land cover.

GIS topology

GIS topology records spatial relationships such as adjacency, connectivity, and containment; it supports network tracing, parcel validation, and detection of gaps or overlaps.

Raster resampling rule

Use nearest-neighbour resampling for categorical rasters to preserve class codes; use bilinear or cubic interpolation for continuous surfaces such as elevation or imagery.

Spatial join

A spatial join transfers attributes from one layer to another based on a spatial relationship such as intersects or within, without necessarily creating new geometry.

Professional negligence

Professional negligence requires a duty of care, a breach of the standard expected of a competent surveyor, causation, and actual loss or damage.

Conflict of interest

A conflict of interest exists when a surveyor's personal, financial, or professional interest could improperly influence judgment; it must be disclosed and managed or declined.

Surveyor adjudication limit

A cadastral surveyor measures and reports boundary evidence but does not decide legal ownership; title and boundary disputes are determined by courts or statutory registries.

Contemporaneous records

Field notes, observation logs, calibration certificates, and plans should be recorded at the time of work and retained to provide traceable evidence of professional decisions.

Statute over instruction

When a client instruction conflicts with surveying law, public safety, or professional standards, the statutory or safety requirement prevails and the instruction should be documented in writing.

SURCON mandate

The Surveyors Council of Nigeria regulates surveying practice by registering practitioners, prescribing standards, accrediting training, and disciplining professional misconduct within its statutory powers.