NSPS Certified Survey Technician Level I key terms

A fixed, known point with an established elevation or position that survey work is referenced to. Crews use it as the starting or closing control for leveling and traverse runs.

A monumented point whose horizontal position, elevation, or both have been determined to a stated accuracy. It anchors subsequent surveys so measurements tie to a common reference frame.

A durable physical marker such as a rebar, pipe, or disk set in the ground to mark a survey point. Its position and description are recorded so it can be found and used later.

A secondary marker placed near a principal monument, often offset a recorded distance and bearing. It helps a crew recover the true corner if the main monument is disturbed or buried.

A sight taken to a known point of reference after the instrument is set up. It establishes the orientation or height of the instrument relative to that known control.

A sight taken to a new or unknown point whose position or elevation is being determined. In leveling it is the rod reading that is subtracted to find the point's elevation.

The elevation of the instrument's line of sight, computed by adding the backsight rod reading to the known elevation of the reference point. Foresight readings are subtracted from it to get new elevations.

A temporary point on which the rod is held while the instrument is moved and reset. It carries the elevation forward between instrument setups without needing a permanent mark.

A method of determining elevation differences by taking backsight and foresight rod readings between points. Successive setups are chained together to carry elevations across long distances or rough terrain.

The vertical distance of a point above or below a chosen reference surface, usually mean sea level or an assumed datum. It is expressed in feet or meters and reported with the datum named.

A reference surface or framework against which positions and elevations are measured. Horizontal and vertical datums must be identified because coordinates and elevations are meaningless without them.

A series of connected survey lines whose lengths and directions are measured to determine the coordinates of successive points. It may be closed back on itself or tied to known control for checks.

The difference between a measured traverse's ending direction and its expected direction based on geometry. A small misclosure indicates acceptable work; a large one signals an error to be found.

The gap between a traverse's computed ending position and its known or starting position. It is compared against an allowable tolerance to judge whether the survey meets accuracy requirements.

An electronic instrument combining an angle-measuring theodolite with an electronic distance meter and onboard computing. It records horizontal and vertical angles plus slope distance to compute point coordinates.

A retroreflector mounted on a pole or tripod that returns the total station's signal for distance measurement. Its height above the point must be measured and entered correctly.

A method of finding distance by timing or phase-comparing a light or microwave signal sent to a reflector and back. It yields slope distance, which is reduced to horizontal and vertical components.

The straight-line distance measured along the inclined line between instrument and target. It must be combined with the vertical angle to compute horizontal distance and elevation difference.

The vertical angle measured from straight up, or zenith, down to the line of sight. It is used with slope distance to compute horizontal and vertical components of a shot.

A graduated vertical staff held on a point to read the height of the line of sight in leveling. Readings are taken on the face of the rod to the nearest hundredth or thousandth of a foot.

A three-legged support that holds an instrument or prism steadily above a point. Its legs are adjusted to level the head and to center the instrument over the mark.

A weighted cord hung from an instrument or rod to indicate a vertical line. It is used to center equipment directly over a survey point when optical or laser plummets are unavailable.

A small telescope in the instrument's vertical axis that lets the operator sight straight down. It is used to center the instrument precisely over a ground mark before measuring angles.

The angle measured in a horizontal plane between two lines of sight, typically turned with a theodolite or total station. It is combined with distances to compute directions and coordinates.

A new monument placed and marked by the survey crew to represent a corner or control position. Its location is determined by measurement and recorded with a description for future recovery.

The written or electronic record of measurements, setups, sketches, and conditions made in the field. They must be legible, complete, and dated because they are the original evidence of the survey.

A bound notebook or digital file used to record field observations in sequence. Entries are made in ink, errors are struck through rather than erased, and pages are numbered for integrity.

A scaled drawing showing boundaries, monuments, and related survey information for a parcel. It is often recorded with a government office and serves as a public record of the survey.

A written legal instrument that conveys an interest in real property from one party to another. It contains a description of the land and must be executed and recorded per local requirements.

The written wording in a deed or document that identifies a parcel of land precisely enough to locate it. It may use metes and bounds, lot and block, or reference to a recorded plat.

A method of describing land by following boundary lines with courses, distances, and monument calls from a point of beginning. It closes back on the starting point to define the parcel.

The starting corner from which a metes and bounds description is traced and to which it must return. Its location and monumentation are critical to correctly retracing the boundary.

The direction of a line stated as an angle east or west of north or south, such as N 45 E. Bearings are measured from a reference meridian and paired with distances in boundary descriptions.

A direction angle measured clockwise from a reference direction, usually north, through a full circle of 0 to 360 degrees. It is common in coordinate geometry and total station work.

A system of planar coordinates defined for each state so that survey positions can be expressed on a grid. Zones and projections are chosen to keep distortion small within each area.

The use of plane coordinates and trigonometry to compute distances, directions, and positions of points. It is the basis for reducing field measurements into mapped coordinates and areas.

A line on a map connecting points of equal elevation. Spacing between contours shows slope steepness, and their shapes reveal ridges, valleys, and other terrain features.

A map that shows both horizontal features and vertical relief, usually through contour lines and spot elevations. It depicts natural and cultural features at a stated scale.

The ratio between a distance on a map or drawing and the corresponding distance on the ground. It may be expressed as a fraction, an equation, or a graphic bar.

Descriptive information about data, such as its source, date, datum, accuracy, and methods. It lets others judge whether the data suits their purpose and how to interpret it.

How close a measured or computed value is to the true value. It differs from precision, which describes how closely repeated measurements agree with one another.

The degree of repeatability or consistency among repeated measurements, regardless of whether they are correct. A precise set of readings can still be inaccurate if a systematic error exists.

Unpredictable variation in measurements caused by small, unavoidable influences in instruments, observers, and conditions. It tends to average out over many observations and is reduced by repetition.

A consistent bias in measurements that shifts results in one direction, such as a mis-set instrument or an incorrect prism height. It does not average out and must be found and corrected.