Surveying Glossary

Most of the definitions presented below are taken in substance from "Definitions of Surveying and Associated Terms" prepared by a joint committee of the American Congress on Surveying and Mapping and the American Society of Civil Engineers, dated 1972. Presented below publication is available from the American Congress on Surveying and Mapping and other sources.


Accuracy is a degree of conformity with a standard. Accuracy relates to the quality of a result and is distinguished from precision, which relates to the quality of the operation by which the result is obtained. see Accuracy and Precision for further information.


An easement is an area of land owned by the property owner, but in which other parties, such as utility companies, may have limited rights granted for a specific purpose.


Encroachment is a structure or part of a structure that occupies the property of another.


Encumbrance is an interest or partial right in real property which diminished the value of ownership but does not prevent the transfer of ownership. Mortgages, taxes, and judgments are encumbrances known as liens. Restrictions, easements, and reservations are also encumbrances, although not liens.


Error is the difference between a measured value and the true value. Error in measurement is inherent but is separate and distinct from a blunder (a mistake).


Exception from a title insurance policy, portions of the land containing encumbrances and in which free and clear title is subject to certain conditions. from a legal description, portions of land which are included in the description of a larger parcel of land but then excluded from it by a subsequent legal description.


Improvement is usually some sort of manmade structure, although perhaps not always a literal "improvement".

Legal Description

A legal description is a method of describing a particular parcel of land in such a way that it uniquely describes the particular parcel and no other. A legal description may be a simple reference to a lot as shown on a subdivision plat or be described by metes and bounds. To be adequate, it should be sufficient to locate the property without oral testimony.


Measurement is an estimated value that is, by its nature, subject to error. A person can count (an absolute value) one hundred beans and get the same quantity as someone else counting one hundred beans. However, if two people each measure (an estimated value) a cup of beans, it is likely that they will have a different quantity of beans. Two surveyors measuring the same distance may obtain different values. Both of the values should be similar, but they will only approach the true theoretical value through repetition and statistical analysis.


A monument is an object placed to mark the physical location of a position. A property corner monument is often a length of an iron rod driven vertically into the ground so that the top is at or below natural grade. A cap identifying the registration number of the surveyor responsible for placing the monument may be placed atop the monument.


Offset in boundary: a point located at the extension of a line and marking the direction of the line. An offset monument may be placed on the extension of a line because the offset position can provide a more durable monument. A common practice is to place offset monuments in a sidewalk or curbhead, as these monuments are less likely to be disturbed than a monument marking the actual position.
in construction: a short distance usually measured at a right angle to a line, to preserve the position of the line when it is anticipated that points marking the line itself would be disturbed.


Precision is the degree of refinement in the performance of an operation or the degree of perfection in the instruments and methods used when making measurements. An indication of the uniformity or reproducibility of a result. Precision relates to the quality of an operation by which a result is obtained, and is distinguished from accuracy, which relates to the quality of the result. see Accuracy and Precision for further explanation.


Right-of-way is a parcel of land granted by deed or easement for construction and maintenance according to a designated use. This may include highways, streets, canals, ditches, or other uses.

Subdivision Plat

A subdivision plat is a legal instrument intended to take a large parcel of land and divide it into smaller parcels of land. A subdivision plat may also create public rights-of-way or easements, and is usually filed with the public real estate records of the county.


Surveying is a blend of several disciplines, from mathematician and law scholar to expert measurer and translator. By interpreting the legal description and applying the science of measurement, the surveyor translates a legal description or construction plans into tangible positions on the ground. These positions then become the basis for construction or for the establishment of a particular location, possibly to show lines of ownership or to document change over time.

Surveying or Land Surveying 

Surveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them commonly practiced by surveyors, and members of various engineering professions. These points are usually on the surface of the Earth, and they are often used to establish land maps and boundaries for ownership, locations like building corners or the surface location of subsurface features, or other purposes required by government or civil law, developers, homeowners for property sales, construction, site planning, land development and permits for new site improvements.

Title Commitment

The title commitment is a commitment to provide title insurance to a parcel of land. The surveyor is interested in the legal description and the exceptions.


Tolerance is a mathematical term indicating the allowable variation from a standard or from specified conditions. It is an indication of the accuracy and the precision of a measurement.

XYZ Coordinates

XYZ coordinate is a grouping of three numbers that designate the position of a point in relation to a common reference frame. In common usage, the X and Y coordinate fix the horizontal position of the point, and Z refers to the elevation.