Glossary of surveying terms a client, an attorney and a field crew each use differently

Surveying has an unusually large stock of words that mean one thing in ordinary speech, something narrower in a deed, and something different again on a jobsite. A client hears accuracy and thinks care. An attorney hears monument and thinks of the document. A rodman hears shot and thinks of the last three seconds. Most of the friction between these groups comes from words, not from disagreement about facts.

The definitions below are grouped by theme. Where a term is commonly misunderstood, the entry says so. None of this is legal advice, and terms that carry statutory meaning vary between jurisdictions.

Field work

Setup

An instrument position from which observations are made. Everything measured from one setup shares that setup's errors, which is why a suspect result is often re-observed from a different setup rather than repeated from the same one.

Occupy

To place the instrument over a known point and measure the instrument height above it. Occupying a point is not the same as merely standing near it; the instrument must be centered over the mark.

Backsight

An observation to a point of known position, used to orient the instrument. If the backsight is wrong, every subsequent measurement from that setup is rotated by the same amount, and the internal geometry will still look perfect.

Foresight

An observation forward to the next point in a sequence. In levelling, the foresight is the rod reading taken on the point whose elevation is being determined.

Side shot

An observation to a detail point that is not part of the control sequence. Side shots carry no check of their own, which is why a mistake in a side shot survives to the drawing unless it is re-observed.

Turning point

In levelling, a temporary point used to carry elevation forward when the instrument must be moved. It is both a foresight from one setup and a backsight from the next, so it must not move between the two.

Traverse

A connected sequence of measured lines forming a route between points. A closed traverse returns to its start or ties to known points, giving a check; an open traverse does not, and provides no way to detect error.

Recovery

Finding an existing monument and confirming its identity and condition. To a client this sounds like a small step; in practice it is often the majority of the field effort on a boundary survey.

Witness monument

A monument set at a known offset from a corner that cannot itself be monumented or is likely to be destroyed. Also called a reference monument. It preserves the ability to re-establish the corner.

Cut and fill

The vertical difference from a stake mark to the design grade. Cut means dig down; fill means build up. Contractors read the cut, not the design elevation, because they cannot see the design surface.

Offset

A perpendicular distance from a reference line or feature. Stakes are set on offset so they survive construction. A stake with no offset written on it is worse than no stake at all.

Reconnaissance

The preliminary visit that establishes access, sky visibility, obstructions, and where control can safely be placed. Skipping it is the fastest way to convert a one-day job into a three-day job.

Instruments

Total station

An instrument combining electronic angle measurement with electronic distance measurement, so a single observation yields horizontal angle, vertical angle and slope distance. A robotic total station is one that tracks and is controlled from the prism, allowing one-person operation.

Theodolite

An instrument that measures horizontal and vertical angles only. Largely superseded by the total station in general practice but still used where high angular precision is required without distance measurement.

Level

An instrument that establishes a horizontal line of sight so height differences can be read on a graduated rod. An automatic level uses a compensator to hold the line horizontal; a digital level reads a bar-coded rod electronically and removes the reading blunder.

Level rod

The graduated staff read through the level. Rod graduations differ between systems, and mixing a rod graduated in feet and decimals with one graduated in feet and inches inside a single run is a well-known source of gross error.

Prism

A corner-cube retroreflector that returns the instrument's beam along the incoming path. Each prism type has a constant offset that must be entered in the instrument; using the wrong prism constant biases every distance by the same amount.

Tribrach

The three-screw base that attaches an instrument or a prism to a tripod and allows precise levelling and centring. A tribrach out of adjustment introduces a centring error at every setup that uses it.

Optical plummet

The sighting device used to center an instrument precisely over a point. A plummet out of adjustment produces a small consistent offset that mimics a real discrepancy in the survey and is easy to blame on something else.

Data collector

The field computer that stores observations, runs the survey routine and holds the job's coordinate data. The raw observation file it records, as distinct from the computed coordinates, is the auditable record of what was actually measured.

GNSS receiver

A receiver using signals from one or more global navigation satellite constellations to determine position. Survey-grade receivers track the carrier phase, which is what makes centimetre-level results possible; consumer receivers do not.

Base and rover

A configuration in which one receiver occupies a known point and transmits corrections to a moving receiver. The rover's results are only as good as the coordinates assigned to the base; a mistyped base coordinate shifts the entire day's work.

RTK

Real-time kinematic positioning, in which corrections are applied as the observation is made so positions are available immediately in the field. A real-time network replaces the individual base with a regional network of permanent reference stations.

Static observation

A GNSS session in which a receiver records data at a fixed point for an extended period for later processing. Longer sessions and changing satellite geometry deliver accuracy that real-time methods cannot match.

Laser scanner

An instrument that sweeps a laser rangefinder to produce a dense point cloud of everything in view. Excellent on structures and complex geometry; blind behind anything, which is why several setups are almost always required.

EDM

Electronic distance measurement. Accuracy is quoted as a constant plus a proportional part, for example 2 mm + 2 ppm, so at 1500 m the expected uncertainty is about 5 mm.

Boundary

Monument

A physical object marking a point on a boundary: an iron pipe, a rebar with cap, a stone, a concrete post, or a natural feature called for in the record. Attorneys sometimes use the word for the document; to a surveyor it is always the physical object.

Corner

A point where boundary lines meet. Note the distinction from monument: the corner is the geometric position, the monument is the object marking it. A corner can exist with no monument, and a monument can exist that no longer marks the corner.

Metes and bounds

A description that traces the perimeter by direction and distance, referencing monuments and adjoiners. Metes are the measurements, bounds are the limits such as a road or a neighbouring tract.

Call

Any element of a description that identifies something: a call for a monument, for an adjoiner, for a course and distance, or for area. When calls conflict, established principles rank them, with physical evidence generally outranking written measurements.

Legal description

The written identification of a parcel used in a conveyance. A street address is not a legal description, and a tax parcel number usually is not either, though some jurisdictions permit reference to one.

Deed

The instrument transferring an interest in land. It contains a description of the land but does not itself establish where that land is on the ground; that determination is the survey.

Easement

A right to use land owned by another for a stated purpose. The land remains the owner's; what is transferred is a right of use. Clients frequently assume an easement means the utility owns the strip, which it usually does not.

Right-of-way

Used two ways. As a property interest it is the right to pass over land, often held by a public body for a road. As a physical thing it is the strip itself. Whether the public holds fee or only an easement varies and matters.

Appurtenant

Attached to and running with the land rather than belonging to a person. An appurtenant easement passes automatically to the next owner of the benefited parcel, which is why easements survive sales that nobody discussed them at.

Encroachment

Something extending across a boundary onto adjoining land: a fence, a shed, an eave, a driveway. The survey reports its existence and extent; whether it must be removed, and what rights it may have created, is a legal question.

Setback

The minimum distance a structure must be from a boundary, imposed by zoning or by a plat restriction. It is a land use limit, not a boundary, and it is administered by the jurisdiction rather than determined by the surveyor.

Adjoiner

An owner or parcel sharing a boundary with the subject parcel. Adjoiner deeds are read as a matter of course in boundary work, because a shared line described from only one side is only half described.

Senior rights

The principle that where a parent tract was divided over time, the earlier conveyance generally takes its full described extent and the later one takes what is left. It is why two adjoining deeds that overlap on paper do not create a shared claim.

Retracement

A survey that follows an earlier survey to re-establish its lines. The retracing surveyor's job is to find the original footsteps, not to improve on them with better measurements.

Original survey

The survey that first created the boundaries, whose monuments control regardless of how the measurements compare with modern ones. The distinction from retracement is the single most consequential idea in boundary practice.

Plat

A drawing of a division of land, recorded in the public records. In some regions the words plat, plan and map are used interchangeably; in others they have distinct local meanings, so confirm which is intended.

Gap and overlap

A gap is a strip described by no adjoining deed; an overlap is a strip described by two. Both arise from independent descriptions written at different times and are among the most common findings in boundary work.

Occupation

The physical evidence of how land is actually used and held: fences, hedges, walls, cultivation, driveways. Occupation is evidence of the boundary, not the boundary itself, though long-standing occupation carries real weight.

Riparian and littoral

Rights relating to land bordering water: riparian for rivers and streams, littoral for lakes and seas. Water boundaries can move with the water, which makes them the most jurisdictionally variable topic in boundary practice.

Computation

Bearing

A direction expressed as an angle from north or south, toward east or west, never exceeding 90°. Written for example as N 42°17′30″ E. Every bearing has a quadrant letter at each end, and dropping one makes the direction ambiguous.

Azimuth

A direction expressed as a clockwise angle from north, from 0° to 360°. The bearing N 42°17′30″ E is azimuth 42°17′30″; S 42°17′30″ W is azimuth 222°17′30″. Computations are usually done in azimuth and reported in bearing.

Latitude and departure

The north-south and east-west components of a line. Latitude is the distance times the cosine of the azimuth, departure the distance times the sine. Careless sign handling on these two components is a leading source of traverse errors.

Inverse

Computing the direction and distance between two known coordinates. The forward computation is the reverse: from a point, a direction and a distance, compute the coordinates of the new point.

Misclosure

The amount by which a survey fails to return to its known starting values. Angular misclosure is expressed in seconds, linear misclosure as a distance and as a ratio: 0.166 ft over a 2847.65 ft perimeter is about 1:17,100.

Closure

Used loosely for both the act of returning to a known point and the quality of that return. A good closure is a necessary check, not proof of correctness; two compensating errors close perfectly.

Precision and accuracy

Precision is repeatability; accuracy is closeness to truth. A total station with a mis-set prism constant is highly precise and consistently wrong. Clients almost always mean accuracy when they say precision.

Blunder

A mistake, as distinct from a random error: a transposed digit, a wrong instrument height, a misidentified point. Blunders are not reduced by taking more measurements and are not handled correctly by adjustment; they must be found and removed.

Least squares adjustment

A statistical adjustment distributing residual error across a network so that the sum of weighted squared residuals is minimised. Its value lies as much in the statistics it reports as in the coordinates it produces.

Station

Distance along an alignment from an origin, written with a plus separating hundreds of feet, so 12+45.67 is 1245.67 ft. Station is measured along arcs through curves, not along the tangents.

Scale factor

The ratio between a distance on the map projection and the corresponding distance on the ground. The combined factor also includes the reduction for elevation; grid distance divided by the combined factor gives ground distance.

Grid and ground

Grid coordinates lie on a map projection; ground distances are what a tape or total station measures. They differ by the combined factor, and mixing them is one of the most common systematic errors in project work.

Datum

The reference surface and framework that coordinates or elevations are expressed relative to. Two correct surveys on different datums will give different numbers for the same monument, which is not an error but must be labelled.

Ellipsoid and geoid

The ellipsoid is a smooth mathematical figure approximating the Earth; the geoid is an equipotential surface of gravity approximating mean sea level. Satellite positioning yields height above the ellipsoid, while elevation that governs drainage is height above the geoid.

Deflection angle

The angle between the extension of the previous line and the next line, measured left or right. Used heavily in route surveying because it is the natural way to describe a change of direction along an alignment.

Degree of curve

A way of expressing curve sharpness instead of radius. Under the arc definition, the degree of curve is 5729.578 divided by the radius, so a 1000.00 ft radius is a curve of 5°43′46″.

Deliverables

Plat of survey

The signed and sealed drawing presenting the surveyor's determination, including monuments found and set, record versus measured values, and the certification. It is the product, and it is meant to be read rather than filed unopened.

Basis of bearings

The statement of what the directions on a drawing are referenced to: a geodetic north, a state plane grid north, a recorded plat, or an assumed direction between two monuments. Without it, a later surveyor cannot tell a real rotation from a difference in reference.

Certification

The surveyor's statement of what was done and to what standard, with a seal and signature. Only the parties named may rely on it, which is why the list of certified parties has to be settled before the document is sealed.

Record of survey

A survey filed in a public repository so that its evidence and measurements are preserved for future surveyors. Requirements for when filing is mandatory vary by jurisdiction.

Cut sheet

The tabulated list of staked points with station, offset, design elevation, stake elevation and cut or fill. It is the record of what was staked and is the first document consulted when a construction dispute arises.

Point file

A list of point numbers with coordinates, elevations and descriptor codes. Simple, portable and durable, which is why it remains the safest way to hand survey data to someone using different software.

Surface model

A digital representation of the ground, usually a triangulated network built from points and breaklines, or a regular grid. The breaklines matter more than the point count, because they force the surface to bend where the ground bends.

Breakline

A line along which the terrain changes slope abruptly, such as a curb face or a ditch centerline. Without breaklines, an interpolated surface cuts across the feature and computed volumes are wrong even when every point is right.

Metadata

The description accompanying the data: datum, geoid model, epoch, units, method, date, accuracy achieved and how it was checked. Data without metadata loses most of its value within a few years, and all of it within a decade.

If one habit is worth taking from this list, it is asking which meaning is intended whenever one of these words appears in a scope of work. Most survey disputes that reach a lawyer began as two people using the same word confidently and differently.