# Parallel Definitions for Land Surveyors

**parallel****—**^{1}Extending in the same direction and everywhere equidistant. as of lines or surfaces**. **^{2}A circle on the surface of the Earth, parallel to the equator and connecting points of equal latitude, or a circle parallel to the primary great circle of a sphere or ellipsoid; also a closed curve approximating such a circle.

**parallel, arc of****—**A part of an astronomic or geodetic parallel.

**parallel, astronomic****—**A line on the surface of the Earth which has the same *astronomic *latitude at every point. Because the deflection of the vertical is not the same at all points on the Earth, an astronomical parallel is an irregular line, not lying in a single plane. The astronomic parallel of 0° latitude is called the “astronomic equator” or the “terrestrial equator.”

**parallel, auxiliary standard **[USPLS]—A new standard parallel or correction line established, when required, for control purposes where original standard parallels or correction lines were placed at intervals of 30 or 36 miles. Auxiliary standard parallels are used in the extension of old surveys and for the control of new surveys.

**parallel, celestial****—**A circle, on the celestial sphere, whose points have the same declination; parallel of declination.

**parallel, geodetic****—**A line on an ellipsoid which has the same geodetic latitude at each point. A geodetic parallel, other than the equator. is not a geodetic (geodesic) line. In form it is a small circle whose plane is parallel to the plane of the geodetic equator.

**parallel, geographic****—**A line on the Earth with the same latitude at each point. The term is applicable to an astronomic as well as a geodetic parallel.

**parallel, standard **[USPLS]—An auxiliary governing line established along the astronomic parallel; initiated at a selected township corner on a principal meridian, usually at intervals of 24 miles from the base line, on which standard township, section, and quarter-section corners are established. These lines were established to limit the convergence of range lines from the south. In many of the surveys made before 1850, standard parallels were run 30, 36. and sometimes even 60 miles apart from the base line. Also called “correction line.”

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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