LA Land Surveyor cheat sheet

Retracement follows the footsteps of the original surveyor; it does not create new boundaries, only locates existing ones.

California priority of evidence: natural monuments, then artificial monuments, then courses and distances, then area; quantity of evidence and harmony of the whole can outweigh a single call.

Original government survey corners are protected; a lost corner is reestablished by proportionate measurement between the nearest existing original corners on the line.

Single proportionate measurement applies to a lost corner on a line; double proportionate measurement is used for a lost corner in the interior where two intersecting lines meet.

A meander line does not mark the water boundary; it is an approximation of the bank, and the actual water boundary is ambulatory.

For a non-riparian lot, area is governed by the calls and monuments; for a riparian lot, accretion and reliction move the boundary with the ordinary high water mark.

Adverse possession and prescriptive easement require distinct elements: actual, open and notorious, exclusive, hostile, continuous for the statutory period (California: 5 years for possession).

Parol evidence may be admitted to explain an ambiguity in a deed but not to contradict or vary unambiguous terms.

California Land Surveyors Act (Business and Professions Code §§8700 et seq.) governs licensure; only a licensed land surveyor may practice land surveying.

A licensed land surveyor may also practice civil engineering only if separately licensed as a civil engineer; the reverse is not true.

Professional negligence standard: the surveyor owes the duty of reasonable care and competence of a professional in the same or similar community.

Statute of limitations for written contracts in California is generally 4 years; oral contracts 2 years; latent defects may extend the period.

Record of Survey (Business and Professions Code §8762) is required when material evidence is found that differs from the record, when a corner is reestablished, or when a subdivision is not shown on a recorded map.

The Record of Survey map must be filed with the county surveyor within 90 days of the survey's completion when required by §8762.

A surveyor must not sign or seal work not performed under their responsible charge; stamping plans reviewed only superficially is a violation.

Ethical obligations: disclose conflicts of interest, maintain confidentiality, and do not accept compensation from more than one party for the same service without consent.

NAD83 (2011) is the current horizontal datum for California; NAD27 is legacy and differs by 10–100 m depending on location.

State Plane Coordinate System in California uses six zones; each zone has a defined projection and a scale factor that must be applied to convert ground distances to grid distances.

Combined factor = elevation factor × grid (scale) factor; ground distance × combined factor = grid distance.

Elevation factor ≈ R / (R + h), where R is the earth radius (≈6,371,000 m) and h is the average orthometric height above the ellipsoid.

NAVD88 is the current vertical datum; NGVD29 is legacy. Orthometric heights differ from ellipsoid heights by the geoid separation N (h = H + N).

UTM zones: California spans zones 10 and 11; UTM uses a transverse Mercator projection with a central meridian scale factor of 0.9996.

Geodetic azimuth is measured from grid north or true north; convergence angle converts between grid and true azimuth.

Latitude/longitude conversions require a datum; mixing NAD27 and NAD83 coordinates in the same computation produces systematic errors.

Total station angle accuracy is specified in seconds (e.g., 2"); distance accuracy is typically ±(2 mm + 2 ppm).

EDM errors: a constant offset (prism constant) and a scale error (ppm) that grows with distance; atmospheric correction uses temperature and pressure.

Horizontal angle measurement uses theodolite/total station; face-left and face-right observations cancel collimation and trunnion axis errors.

Leveling loop misclosure is distributed proportionally to the number of setups or distances; allowable misclosure often expressed as C√km.

GNSS static accuracy improves with longer observation sessions; RTK accuracy is typically 1–2 cm horizontal and 2–4 cm vertical.

Traverse closure: linear error of closure = √(ΔE² + ΔN²); relative precision = closure / perimeter.

Instrument leveling: check bubble, set up over point, and perform a two-peg test to verify collimation error.

Taping corrections include temperature, tension, sag, and slope; each correction is added or subtracted from the measured length.

Scale of a vertical aerial photograph = f / H, where f is focal length and H is flying height above ground.

Relief displacement on a vertical photo increases with radial distance from the principal point and with object height; it is zero at the nadir.

Stereo overlap for mapping is typically 60% forward overlap and 20–30% sidelap.

Ground sample distance (GSD) = pixel size × flying height / focal length.

Orthophoto rectification removes relief displacement and tilt, producing a uniform-scale image.

LiDAR point cloud classification separates ground, vegetation, and structures; a DEM derived from ground returns represents bare earth.

Photogrammetric triangulation (bundle adjustment) solves camera positions and object coordinates simultaneously from overlapping imagery.

NDVI = (NIR − Red) / (NIR + Red); values near 1 indicate healthy vegetation, near 0 indicate bare soil or water.

Map scale is the ratio of map distance to ground distance; a 1:24,000 map has 1 inch = 2,000 feet.

Large-scale maps show more detail over smaller areas; small-scale maps cover larger areas with less detail.

Contour interval is the vertical distance between adjacent contour lines; index contours are heavier and labeled.

Hachures indicate depressions; closed contours with hachures point inward.

Map projections distort area, shape, distance, or direction; no projection preserves all four.

A GIS map must state datum, projection, and units; mixing layers with different datums without transformation causes misalignment.

Legends, north arrows, scale bars, and metadata are required elements of a professional map.

Generalization reduces detail for smaller scales; it includes simplification, smoothing, aggregation, and displacement.

Subdivision Map Act is codified in Government Code §§66410 et seq.; it governs the division of land in California.

A tentative map must be filed with the local agency; approval is discretionary and subject to the Subdivision Map Act and local ordinance.

A parcel map is required for subdivisions creating four or fewer lots; a final map is required for five or more lots (with exceptions).

A final map must be based on a field survey and be tied to a Record of Survey or official monuments.

The Subdivision Map Act requires dedications, reservations, and improvements as conditions of approval; exactions must have a reasonable relationship to the project.

A lot line adjustment (four or fewer parcels) is processed under Government Code §66412(d), not as a subdivision.

A certificate of compliance may be issued to legalize an existing parcel that does not conform to current standards.

Coastal and hillside subdivisions may require additional geologic and environmental review under CEQA.

Construction staking transfers design positions to the field using control points, offsets, and grades.

Benchmarks establish vertical control; a temporary benchmark must be tied to a published datum.

Slope staking sets grade stakes at a specified offset from the centerline; cut/fill is the difference between design and existing grade.

Horizontal control for construction is typically a traverse or GNSS network with stated accuracy; check shots verify the setup.

As-built surveys document constructed conditions and are compared to design for payment and acceptance.

Machine control uses 3D models and GNSS or total station to guide grading equipment; accuracy depends on base station and model quality.

Tolerance for construction layout is often specified in the contract (e.g., ±0.05 ft for structures, ±0.10 ft for grading).

Safety and traffic control plans are required for work within public right-of-way.

Vector data models represent points, lines, and polygons; raster models represent continuous surfaces as cells.

Topology defines spatial relationships (adjacency, connectivity, containment) and prevents gaps and overlaps in vector data.

A coordinate system in GIS includes datum, projection, and units; reprojecting on the fly can introduce error if not done correctly.

Attribute joins link tables by a common key; a one-to-many join can duplicate features.

Spatial analysis includes buffer, overlay (union, intersect), and proximity; overlay requires consistent coordinate systems.

Raster resolution (cell size) controls detail; smaller cells increase storage and computation.

Metadata documents source, accuracy, projection, and processing history; it is required for data sharing and quality control.

Geodatabase feature classes can enforce domains and subtypes to maintain data integrity.