SURCON Professional cheat sheet

A cadastral parcel is defined by boundary geometry, a unique identifier, and legal or administrative attributes; coordinates alone do not establish title.

Boundary re-establishment evidence hierarchy: undisturbed original monument, then original survey records, then occupation evidence, subject to the governing statute.

Closed traverse linear misclosure: e = sqrt(eN^2 + eE^2); relative precision = perimeter / e.

Polygon area by coordinates: A = 0.5 * |sum(X_iY_i+1 - X_i+1Y_i)| for i = 1..n with point n+1 equal to point 1.

Registration sequence: survey plan, lodgment, examination and approval, entry in land register, issuance of certificate or title.

General boundaries follow physical features; fixed boundaries use coordinated, monumented geometry; the applicable type is determined by statute or registry rules.

Overlaps between parcel polygons indicate conflicting surveys; gaps may be roads, reserves, or error and require investigation before registration.

Cadastral coordinates must be tied to geodetic control and meet the accuracy class specified by the land registry or cadastral standard.

Ellipsoid flattening f = (a - b)/a; first eccentricity squared e^2 = 2f - f^2.

Geodetic to Cartesian: X = (N + h) cos(phi) cos(lambda), Y = (N + h) cos(phi) sin(lambda), Z = (N(1 - e^2) + h) sin(phi).

Prime vertical radius N = a / sqrt(1 - e^2 sin^2(phi)); meridian radius M = a(1 - e^2) / (1 - e^2 sin^2(phi))^(3/2).

Geoid undulation relation: N = h - H, where h is ellipsoidal height and H is orthometric height.

A seven-parameter Helmert transformation uses three translations, three rotations, and one scale factor; residuals indicate datum or network distortion.

Projection scale factor k = grid distance / ellipsoidal distance; combined factor accounts for projection and elevation, with UTM central-meridian k0 = 0.9996.

GNSS relative positioning uses differenced carrier-phase observations; baseline accuracy depends on ambiguity resolution, satellite geometry, and atmospheric error control.

Deflection of vertical has two components; Laplace azimuth constrains astronomic and geodetic azimuths at a Laplace station.

Vertical photo scale S = f / H_agl = photo distance / ground distance.

Relief displacement on a vertical photo: d = r*h/H, where r is radial distance from nadir, h object height, H flying height above datum.

Ground sample distance GSD = pixel size * H_agl / f.

Parallax difference between conjugate points indicates height difference; larger parallax corresponds to higher objects on a vertical photograph.

Endlap commonly 60 percent and sidelap 20 to 30 percent for aerial mapping; overlap determines base-height ratio and vertical accuracy.

Interior orientation recovers focal length and principal point; exterior orientation recovers six pose parameters for each image.

Orthophoto removes relief displacement and tilt using a DEM; DSM includes surface objects while DTM represents bare earth.

NDVI = (NIR - Red)/(NIR + Red); values near +1 indicate dense vegetation and near 0 or negative indicate non-vegetated surfaces.

Remote sensing resolution categories are spatial, spectral, temporal, and radiometric; the limiting category controls detectable detail.

Representative fraction 1:50,000 means one map unit represents 50,000 ground units; larger scale means smaller denominator and more detail.

Conformal projections preserve local angles; equal-area projections preserve area; equidistant projections preserve distance from specified standard points or lines.

Geographic coordinates use latitude and longitude on a datum; projected coordinates use easting and northing in a map projection; reprojection does not improve source accuracy.

Topology encodes adjacency, connectivity, and containment; it supports network tracing and detection of gaps, overlaps, and dangling edges.

Vector overlay operations include union, intersection, clip, and erase; raster overlay uses map algebra on aligned cells.

Classification choices: equal interval for uniform ranges, quantile for equal counts, natural breaks for clustered data, standard deviation for deviation from mean.

Spatial join transfers attributes by a spatial predicate such as intersects or within; overlay creates new geometry and attributes.

Resampling: nearest-neighbour preserves categorical class codes; bilinear or cubic interpolation suits continuous surfaces but alters values.

Generalization operators include simplification, smoothing, aggregation, displacement, and exaggeration; selection depends on scale and map purpose.

Professional negligence elements: duty of care, breach of the standard of a competent surveyor, causation, and actual damage.

Ethical practice requires competence, impartiality, confidentiality, disclosure of conflicts, and accurate representation of qualifications and results.

A cadastral surveyor measures and reports boundary evidence; legal ownership and boundary disputes are determined by courts or statutory registries.

Falsification, unauthorized alteration, or improper use of a survey plan can constitute professional misconduct and may also be a statutory offence.

Contemporaneous field notes, observation logs, calibration certificates, and signed plans provide traceable evidence of professional decisions.

When client instructions conflict with statute, public safety, or professional standards, the legal or safety requirement prevails and the conflict is documented.

A survey contract should define scope, deliverables, accuracy, fees, liability, data rights, and dispute resolution before work begins.

SURCON regulates surveying in Nigeria through registration, standards, accreditation, and discipline within its statutory mandate.