Control Definitions for Land Surveyors

control, basic—In general, coordinated and correlated position data forming a framework to which detail surveys are adjusted. Basic control may be either horizontal or vertical; it is usually executed with greater precision and accuracy than is required for dependent surveys. Also the point or points permanent in character within a network of basic control, for which the coordinates and/or elevation to a specific accuracy are known and which are used as origin and closure for making a control survey, or for making an engineering, cadastral, or other survey.

control, cadastral [USPLS]—Lines established and marked on the ground by suitable monuments, which are used as starting and closing points in surveys of the public domain of the United States. The primary control of the public land surveys of the United States consists of base lines, standard parallels (correction lines), principal meridians, and guide meridians.

control, geodetic—A system of horizontal and/or vertical control stations that have been established and adjusted by geodetic methods and in which the shape and size of the earth (geoid) have been considered in position computations.

control, horizontal-1 Physical stations which have known horizontal coordinates (longitude and latitude), and which can be used to provide horizontal coordinates for other surveys. 2 A control station or stations whose horizontal coordinates have been determined. 3 The geometric data relating to the horizontal coordinates of a control station.

control, level—A series of bench marks or other points of known elevation, established throughout a project.

control, national control survey nets—The two control survey nets being extended over the United States by the National Ocean Service for the control of nautical charts and topographic maps, arid comprising horizontal and vertical components.

control, photo—Any station in a horizontal and vertical control system that is identified on a photograph and used for correlating the data shown on that photograph, also termed photocontrol point, picture control point, and ground control point.

control, photogrammetric—Control established by photogrammetric methods as distinguished from control established by ground or other methods.

control, supplemental—Points established by subordinate surveys, to relate aerial photographs used in mapping with the system of geodetic control.

control, vertical-1 Physical stations which have known elevations, and which can be used to provide elevations for other surveys. 2 The elevations, or approximations thereto, associated with control points.

control document—Any legal document which affects the ownership or use of public lands or resources.

control document index—Microphotographic copies of control documents mounted in aperture tabulating cards arranged by state, meridian, and township.

control network—A survey network composed of control stations.

control point [PHOTOGRAMMETRY]—Any station (in a horizontal and/or vertical control system) identified on a photograph and used to aid in fixing the attitude and/or position of a photograph or group of photographs; supplemental control point, photo control point, picture control points, or ground control point.

control station—A point on the ground whose position (horizontal, vertical) is used as a base for a dependent survey.

control station, horizontal—A station whose position has been accurately determined in X and Y, or latitude and longitude.

control survey—See survey, control.

control survey classification—A series of designations to classify control surveys according to their precision and accuracy. See also Appendix A, Standards Geodetic Control Surveys.

Source: NSPS “Definitions of Surveying and Associated Terms\”, used with permission.

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