SURCON Technologist cheat sheet

Traverse closure: linear misclosure = sqrt(ΔE² + ΔN²); relative precision = misclosure / total traverse length, expressed as 1:N (e.g., 1:10,000).

Bowditch (compass) rule distributes misclosure proportionally to leg length; the transit rule distributes it proportionally to the northing/easting change of each leg.

Angular misclosure for an n-sided closed traverse = sum of observed interior angles − (n−2)×180°; permissible error commonly set as a×√n where a is the instrument's specified seconds per setup.

Resection (three-point problem) fixes an unknown station from three known points; the danger circle is the locus of positions where the three points lie on one circle, giving an indeterminate solution.

Horizontal curve: T = R tan(Δ/2); L = RΔ (Δ in radians) = 100Δ/D where D is degree of curve; M = R(1/cos(Δ/2) − 1).

Vertical curve elevation: y = y_BVC + g1x + ((g2−g1)/2L)x², with x measured from the BVC and grades as decimals.

Contour interval is chosen from map scale and terrain relief; contours crossing a stream form a V pointing upstream, and contours never cross except at an overhang or cliff.

GNSS RTK horizontal accuracy is typically 10 mm + 1 ppm (and roughly double vertically); fix quality degrades with PDOP, multipath, and loss of correction link.

Torrens registration: title is registered and guaranteed by the state, so the register is conclusive evidence of ownership rather than the deed itself.

Boundary retracement principle: follow the original monument first, then bearings and distances, then area, then adjoining parcel lines, in that order of precedence.

Adverse possession requires open, notorious, exclusive, continuous, and hostile possession for the statutory period; it does not extinguish a registered Torrens title in most Torrens jurisdictions.

A metes-and-bounds description must close; the record misclosure is checked before accepting the description, and area is computed by the coordinate (shoelace) method.

Easement vs. fee: an easement conveys a right of use, not ownership; the servient tenement remains in the owner's title.

Lot-and-block and parcel-identifier systems link the cadastral map to the land register; the cadastral index map is not itself the legal evidence of title.

Riparian and littoral boundaries follow the ordinary high-water mark or thread of the stream, depending on jurisdiction; accretion is gradual and belongs to the riparian owner, avulsion does not.

Geodetic vs. geocentric latitude: geodetic latitude is the angle between the ellipsoid normal and the equatorial plane; geocentric latitude is measured from the ellipsoid center, differing by up to about 11.5 arcminutes.

Ellipsoid parameters: flattening f = (a − b)/a; first eccentricity e² = 2f − f²; radius of curvature in the meridian M = a(1−e²)/(1−e²sin²φ)^(3/2).

WGS84 and GDA2020 are geocentric datums; transformations between them require a 7-parameter Helmert (3 translations, 3 rotations, scale) or a time-dependent plate-motion model.

Geoid undulation N relates ellipsoidal height h and orthometric height H by h = H + N; GNSS gives h, leveling gives H.

UTM: 60 zones of 6° longitude, central meridian scale factor 0.9996, false easting 500,000 m; the scale error grows with distance from the central meridian.

Map projection distortion: conformal projections preserve angles and local shape but not area; equal-area projections preserve area but distort shape.

DOP: PDOP² = HDOP² + VDOP²; a PDOP below about 4 is generally needed for reliable RTK fixes.

Coordinate transformation: a minimum of 2 control points for a 4-parameter (2D Helmert) and 3 for a 6-parameter (3D) similarity transformation; residuals reveal control quality.

A surveyor signs and seals only work performed by themselves or under their direct supervision; sealing work outside one's competence is a disciplinary offence.

Conflict of interest must be disclosed in writing before accepting an engagement; a surveyor may not act for both parties in the same boundary dispute without informed consent.

Records, field notes, and coordinates are retained for the statutory period (commonly 7 years or the jurisdiction's specified term) and are the property of the client or the public record as defined by law.

Boundary opinions are professional opinions, not legal determinations; the surveyor reports evidence and does not adjudicate title.

Confidentiality: client information may be disclosed only with consent or where required by law, subpoena, or public safety.

Continuing professional development is a condition of registration renewal in most jurisdictions; falsifying CPD records is misconduct.

Advertising and fees must not be misleading; contingency fees tied to a boundary outcome are generally prohibited as compromising independence.