PA Land Surveyor key terms

The direction of a survey line stated as an angle from north or south toward east or west, always 90 degrees or less and written with both letters, such as N 45 E.

A direction measured clockwise from a fixed reference meridian, usually north, running from 0 to 360 degrees. Unlike a bearing, it is a single continuous angle with no quadrant letters.

A reference line of constant direction from which angles are measured, commonly true north, magnetic north, grid north, or an assumed line. The chosen meridian must be stated because bearings and azimuths depend on it.

The horizontal angle between true north and magnetic north at a given place and time. It changes slowly with location and date, so old magnetic bearings must be corrected before being compared with current true directions.

The north-south component (latitude) and east-west component (departure) of a course, computed from its length and bearing or azimuth. Summing them around a closed traverse reveals the linear misclosure.

A survey in which lengths and directions of connected courses are measured and coordinates are computed from them. A closed traverse returns to its start or a known point, allowing checks on angular and linear error.

The difference between the sum of measured interior or deflection angles in a closed figure and the geometrically required sum. It is distributed among the angles before coordinates are computed.

The length of the vector formed by the summed latitudes and departures of a closed traverse, representing total positional error before adjustment. It is often expressed as a relative precision such as 1 part in 10,000.

A traverse adjustment method that distributes latitude and departure errors in proportion to each course length, so longer courses receive larger corrections. It is commonly applied when angular and distance errors are of similar relative magnitude.

A system of planar coordinates defined separately for each state or zone, based on a map projection of the ellipsoid. Coordinates are in feet or meters and require a scale and convergence correction from ground distances.

A mathematical transformation that flattens positions on the curved earth onto a plane. Every projection distorts some combination of distance, area, shape, or direction, so surveyors apply scale factors to convert between ground and grid.

The ratio between a distance on the projection grid and the corresponding distance on the reference ellipsoid at a given location. It varies across a zone and must be combined with elevation factor to reduce ground distances to grid.

The ratio of the ellipsoid radius to the sum of that radius and the average site elevation, used to reduce horizontal ground distances to the ellipsoid. Surveys far above sea level need this correction to match grid coordinates.

A mathematically defined oblate spheroid that approximates the shape of the earth, used as the reference surface for geodetic coordinates. Different regions historically adopted different ellipsoids, such as Clarke 1866 or GRS80.

The equipotential surface of the earth's gravity field that best matches mean sea level, extended through the continents. Orthometric heights are measured relative to it, and its separation from the ellipsoid is the geoid height.

The elevation of a point above the geoid, roughly equivalent to height above mean sea level. It differs from ellipsoid height by the geoid separation and is the elevation used in most engineering and floodplain work.

A permanent, stable monument of known elevation or coordinates used as a reference for leveling and other surveys. Its published data include the datum, epoch, and accuracy, which must be checked before use.

A reference surface or framework against which positions and elevations are measured, such as NAD83 for horizontal coordinates or NAVD88 for elevations. Mixing datums without transformation introduces systematic offsets.

A method of determining elevation differences by reading a graduated rod at two points with a level instrument set between them. Careful setup and balanced sight distances reduce instrument and curvature errors.

The discrepancy between a measured value and its known or theoretically required value at the end of a survey loop or traverse. It is compared against an allowable tolerance to judge whether the work is acceptable.

Two combined effects that make a level sight read too high over long distances: earth curvature drops the target, while atmospheric refraction bends the line of sight downward. Balancing foresight and backsight distances cancels most of the error.

A leveling technique for crossing wide rivers or deep valleys, where readings are taken from both banks and averaged to cancel curvature, refraction, and instrument adjustment error. It is used when sight distances cannot be balanced.

An electronic instrument combining an electronic theodolite with an electronic distance meter and onboard computer. It measures horizontal and vertical angles and slope distances, and can compute coordinates and stakeout positions.

Determination of distance by timing or phase comparison of a modulated light or microwave signal traveling to a reflector and back. The result depends on atmospheric conditions and instrument and prism constants.

A fixed offset added to or subtracted from an electronic distance measurement to account for the path length inside a reflector and its mounting. Using the wrong constant shifts every measured distance by that amount.

An adjustment applied to electronic distance measurements because light speed varies with air temperature, pressure, and humidity. Instruments use entered values, and errors in those values produce scale errors in measured distances.

A constellation-based positioning technology, including GPS, that computes receiver position from ranging signals of multiple satellites. Survey-grade use requires careful observation, correction services, and awareness of multipath and obstruction.

A GNSS technique in which carrier-phase corrections from a base station are radioed to a rover, giving centimeter-level positions in the field. Accuracy degrades as the baseline length between base and rover increases.

A GNSS or distance-measurement error caused by signals reflecting off buildings, water, or terrain and arriving at the antenna by more than one path. It is reduced by antenna design, site selection, and longer observation times.

The reference framework that fixes the position and orientation of a coordinate system relative to the earth, such as NAD83 or a newer realization. Coordinates from different horizontal datums are not directly interchangeable.

A physical object set to mark a survey point, such as a rebar with cap, pipe, or concrete post. Its position, type, and condition are recorded so later surveys can recover and rely on it.

A point that defines the boundary of a parcel, such as a property corner or a section corner in the public land survey system. Corners are legally significant and their evidence controls boundary location.

The rectangular system of land subdivision in much of the United States, using principal meridians, baselines, townships, ranges, and sections. Section corners and subdivision-of-section lines carry legal weight in boundary retracement.

A legal doctrine by which a person can gain title to land through open, notorious, hostile, continuous, and exclusive use for a statutory period. It can override record boundaries and must be considered in boundary disputes.

A right held by one party to use another's land for a specific purpose, such as access, utilities, or drainage. It does not transfer ownership but restricts the servient parcel and appears on surveys as an encumbrance.

Acquisition of an easement or right by long, open, continuous, and adverse use, similar in concept to adverse possession but creating a use right rather than title. The required period is set by state law.

Rights of owners of land bordering a watercourse, including reasonable use of water and access. Boundaries along navigable or non-navigable waters follow state-specific rules that may place the line at the thread or ordinary high water.

The average height of high tides over a specified period, often used as the boundary line for tidal navigable waters. State law determines whether it or another line controls ownership limits.

A record that a monument was set at a described position and is to be held as the corner, often used when the point cannot be physically occupied or when later work will establish it. It documents the surveyor's intent.

The boundary as described in deeds, plats, and other recorded documents, which may differ from what exists on the ground. Retracement surveys must weigh record calls against monument evidence and occupation.