OR Land Surveyor key terms

The federal system that divides most of the United States into a grid of six-mile-square townships referenced to principal meridians and base lines, further split into one-mile-square sections and fractional lots.

The north-south reference line from which township numbering east and west begins within a PLSS survey area. Each meridian governs its own base line and set of townships.

The east-west reference line that, together with a principal meridian, anchors township numbering north and south in the Public Land Survey System.

A PLSS unit nominally six miles on each side containing 36 sections, identified by its position north or south of the base line and east or west of the principal meridian.

A nominally one-mile-square PLSS unit containing 640 acres. Sections are numbered 1 through 36 in a boustrophedon pattern beginning at the northeast corner of the township.

The physical object, such as a marked stone, iron pipe, or concrete post, that marks a PLSS corner. Its position and accessories control the location of the legal boundary.

A monument placed away from an inaccessible or obliterated corner, at a known offset and bearing, used to reestablish the true corner position by reference measurements.

A physical object set to mark a boundary corner or reference point. In boundary law, an original monument generally controls over distances and bearings written in the deed.

Physical or documentary indications of where a boundary was originally established, including monuments, blazes, bearing trees, occupation lines, and field notes. Courts weigh such evidence when resolving disputes.

A tree marked with a blaze and scribed with the corner information, recorded in the original survey notes to help relocate a corner whose monument has been destroyed or disturbed.

A boundary description method that states courses and distances, usually beginning at a known point of beginning and returning to close, often following natural features and called-for monuments.

The starting point of a metes-and-bounds description from which all subsequent courses are run. The description must close back to this point to enclose the parcel.

A written instrument that conveys an interest in real property. Its property description defines the land conveyed, and the deed's language is interpreted under boundary-law rules.

The condition in which a traverse or boundary description returns to its starting point within an acceptable misclosure. Poor closure signals measurement or drafting error.

A doctrine by which a person who openly, notoriously, exclusively, and continuously occupies another's land for the statutory period may acquire title, subject to state-specific requirements.

A nonpossessory right to use another person's land for a specific purpose, such as access or utilities. It may be appurtenant to a parcel or held in gross.

A series of connected survey lines whose lengths and directions are measured to establish horizontal positions. Closed traverses begin and end on known points for error checking.

A horizontal direction angle measured clockwise from a chosen reference meridian, usually north, through 360 degrees. Azimuths are common in modern survey computations.

A direction expressed as an angle east or west of north or south, between 0 and 90 degrees, with a quadrant label such as N45E. Bearings appear in many deed descriptions.

The north-south (latitude) and east-west (departure) components of a course, computed from distance and bearing or azimuth. Summing them reveals traverse misclosure.

An electronic instrument combining an electronic theodolite with an electronic distance meter and onboard computer, used to measure angles and distances and compute coordinates in the field.

A method of measuring distance by timing or phase-comparing a modulated light or microwave signal traveling to a reflector or target and back, with atmospheric corrections applied.

A correction added to or subtracted from an EDM measurement to account for the offset between the instrument's reference point and the reflector's effective optical center.

A satellite-based positioning system such as GPS, GLONASS, Galileo, or BeiDou. Survey-grade receivers use carrier-phase observations and differential corrections to reach centimeter accuracy.

A GNSS surveying technique in which carrier-phase corrections from a base station are transmitted to a rover, yielding centimeter-level positions in real time in the field.

A mathematical model defining the size, shape, and orientation of the Earth and the origin of a coordinate system. Coordinates are meaningless unless the datum is stated.

A mathematically defined surface approximating the shape of the Earth, used as the reference for horizontal geodetic coordinates. Common examples include GRS80 and WGS84.

The equipotential surface of the Earth's gravity field that approximates mean sea level. Orthometric heights are measured relative to it.

A system of planar coordinate zones defined for each state, based on a map projection, that lets surveyors record positions in a common grid with minimal distortion.

A mathematical transformation that converts positions on the curved Earth surface to a flat plane, introducing scale distortion that must be accounted for in precise surveys.

The ratio between a distance on a projected grid and the corresponding distance on the reference ellipsoid or at ground elevation. Used to reduce ground measurements to grid.

A stable monument with a known elevation referenced to a vertical datum, used as a starting or check point for leveling and vertical control.

A method of determining elevation differences by reading a graduated rod at two points through a leveling instrument and subtracting backsight from foresight readings.

A line on a map connecting points of equal elevation. Contours show terrain shape, and their spacing indicates slope steepness.

A survey that locates natural and cultural features and determines elevations to depict the shape of the land, often producing contour maps and digital terrain models.

A drawing of a survey showing boundaries, monuments, and related data, often recorded with a government office to provide public notice of parcel configuration.

A statistical method that distributes random measurement error among observations so the sum of squared residuals is minimized, yielding the most probable coordinate values.

The difference between an observed value and its adjusted or computed value. Residuals help identify outliers and assess the quality of a survey adjustment.