S+SNZ Spatial Measurement cheat sheet

Net residential density = dwellings ÷ net developable area (excludes roads, reserves, stormwater land); gross density includes all site land.

Movement hierarchy: arterial roads carry through traffic, collectors distribute, local roads give access; design speed and carriageway width decrease down the hierarchy.

Intersection sight triangles are measured along each approach and kept clear of obstructions above about 1.0 m; required leg length increases with approach speed.

Earthworks balance: compare cut volume × bulking factor against fill volume × compaction factor; an unbalanced site needs import, disposal or a re-graded design.

Finished floor levels are set above the design flood level plus freeboard (commonly 0.3–0.5 m) and above surrounding ground with fall away from the building.

Accessible routes: maximum longitudinal gradient 1:20, ramps no steeper than 1:14 with landings and handrails, cross-fall limited to about 1:40.

Street enclosure is described by the building-height-to-street-width ratio; ratios between about 1:1 and 1:3 give comfortable pedestrian-scale enclosure.

Post-development stormwater peak flows are controlled to pre-development rates using detention, with first-flush treatment for contaminant removal.

Tight kerb radii and short crossing distances reduce vehicle turn speeds and pedestrian exposure at local road intersections.

Section 5 RMA 1991 purpose: enabling people and communities to provide for wellbeing while sustaining resources to meet the foreseeable needs of future generations.

Activity classes run permitted, controlled, restricted discretionary, discretionary, non-complying, prohibited; each class carries different consent and assessment tests.

Section 104D gateway for non-complying activities: consent may be granted only if adverse effects are minor, or the activity is not contrary to objectives and policies.

Consent types include land use, subdivision, water permit, discharge permit and coastal permit; applications require an assessment of environmental effects under Schedule 4.

National direction (National Policy Statements, National Environmental Standards, National Planning Standards) must be given effect to in regional and district plans.

Designations under sections 168–189 give requiring authorities rights to use land for public works; an outline plan may be required before construction.

Archaeological sites (generally pre-1900) require an authority from Heritage New Zealand Pouhere Taonga before modification or destruction.

Effects assessment covers actual, potential, temporary and cumulative effects; the mitigation hierarchy runs avoid, remedy, mitigate, then offset or compensate.

Notification decisions follow sections 95A–95G: public, limited or no notification, with affected-person and trade-competition tests.

Average end area volume: V = (A1 + A2)/2 × L, where A1 and A2 are cross-sectional areas at chainages separated by distance L.

Prismoidal formula: V = L/6 × (A1 + 4Am + A2), used where sections change in shape as well as area.

Level book check: sum of backsights minus sum of foresights equals last reduced level minus first reduced level.

Grade percentage = (rise or fall ÷ horizontal distance) × 100; a 2 per cent grade rises 2 m in 100 m.

Total station setting out converts slope distance to horizontal using the vertical angle, then pegs by angle-and-distance from control or by offsets from a string line.

Batter slopes are stated as vertical:horizontal; the batter-ground intersection is found by trial along successive cross-sections from the design formation.

Pipe setting out controls invert level, grade and cover: minimum cover, design gradient and manhole invert levels are checked at each structure.

Cross-section areas over irregular ground are computed by the trapezoidal rule, summing strip widths multiplied by average heights.

As-built surveys compare constructed position and level with design, checked against specified tolerances such as ±25 mm for pipe inverts.

GNSS needs at least four satellites for a 3D position plus receiver clock; five or more improves ambiguity resolution and reliability.

Dilution of precision: lower is better; PDOP below about 6 is commonly required for RTK, with HDOP governing horizontal quality.

GNSS error sources include ionosphere, troposphere, multipath, orbit and clock errors; differencing between receivers and satellites removes most common-mode error.

RTK accuracy degrades as baseline length increases; network RTK (VRS) extends effective coverage by modelling atmospheric delay.

Total station reduction: horizontal distance = S·sin z and vertical component = S·cos z, where S is slope distance and z the zenith angle.

Traverse angular misclosure is compared with an allowable value (often proportional to the square root of the number of angles) before distribution.

Compass (Bowditch) rule distributes traverse misclosure proportionally to leg length for both coordinates.

Curvature and refraction combined correction is about 0.067 D² metres with D in kilometres, subtracted from the staff reading; refraction is roughly one-seventh of curvature.

Ground distance = grid distance ÷ combined scale factor, where the combined factor is the projection scale factor multiplied by the elevation factor.

Parcels are defined by survey marks and the cadastral survey dataset lodged with LINZ; the title diagram depicts, but does not itself define, the boundary.

Reinstatement evidence hierarchy: original marks, then undisturbed marks, then occupation consistent with the record, then record measurements, then uncoordinated position.

The Rules for Cadastral Survey 2010 set accuracy standards, mark requirements, and the content and form of cadastral survey datasets.

Horizontal datum is NZGD2000; vertical datum is NZVD2016; NZTM2000 is used for projected mapping coordinates.

Boundaries are defined by bearing (azimuth) and distance vectors from the record; permitted misclose depends on survey class and location, with urban tolerances tighter than rural.

Easements, covenants and encumbrances are registered against titles and shown on plans; they burden or benefit land without transferring ownership.

Unit title boundaries are defined by a unit plan under the Unit Titles Act 2010; cross-lease boundaries derive from a lease of part of the fee simple with a flat plan.

Marks may be geodetic (PRN) or cadastral (pins, pipes, plaques); disturbed marks must be checked, reinstated or reported with supporting evidence.

Stated parcel area is indicative only; where area and boundary dimensions conflict, the dimensions and marks govern.

Soundings are reduced to chart datum, normally Lowest Astronomical Tide in New Zealand, so charted depths are rarely less than actual depth.

Reduced depth = measured depth below transducer + transducer draft + height of tide above chart datum.

Tide corrections come from a tide gauge or predicted model; bar checks before and after survey verify draft and sounder calibration.

Multibeam swath width = 2 × depth × tan(θ/2); a 120-degree system covers roughly 3.5 times the water depth.

Sound speed in seawater is about 1500 m/s and varies with temperature, salinity and pressure; sound velocity profiles correct refraction of the beams.

IHO S-44 defines survey orders (Exclusive, Special, 1a, 1b, 2) with corresponding total horizontal and vertical uncertainty limits.

Positioning uses GNSS RTK or PPK for the vessel and USBL or LBL acoustic systems for ROV, towed body and diver positions.

Full multibeam coverage is required for navigational surveys; single beam lines are spaced to give 10–20 per cent overlap between adjacent lines along the seabed.

Vertical uncertainty budget includes tide, draft, sound velocity, and residual heave, roll and pitch errors.

NZTM2000 is EPSG:2193, a Transverse Mercator projection with central meridian 173°E, scale factor 0.9996, false easting 1600000 and false northing 10000000.

NZGD2000 geographic coordinates are EPSG:4167; WGS84 geographic is EPSG:4326; transformations between them are handled by PROJ pipelines.

Vector topology rules include must not overlap, must not have gaps, must not self-intersect and must be covered by; validation checks enforce these before analysis.

Raster cell size sets the spatial resolution and area precision; each cell value represents the whole cell, so areas are quantised.

Common overlay operations are clip, intersect, union and erase; buffer and dissolve operate on single layers by proximity or attribute.

A relational join matches records on a shared key; a spatial join matches records by geometric predicate such as intersects, within or contains.

DEM stores ground surface elevation; DSM includes buildings and vegetation; DTM is a bare-earth model produced by classifying and removing above-ground LiDAR returns.

Positional accuracy is reported as RMSE in horizontal and vertical components, and dataset quality is documented in metadata following ISO 19115.