Adjustment Definitions for Land Surveyors

adjustment1 A process designed to remove inconsistencies in measured or computed quantities by applying derived corrections to compensate for random, or accidental errors, such errors not being subject to systematic corrections. 2 Bringing the movable parts of an instrument or device more nearly into proper relationship and fit. 3 The positioning of public land lines on the topographic map to indicate their true, theoretical, or approximate location relative to the adjacent terrain, and culture, by reconciling the information shown on BLM (Bureau of Land Management) plats and field records with the ground evidence of the location of the lines.

adjustment, angle method—In traverse measurement, method of adjustment of observations which determines corrections to observed angles. The angle method of adjustment may be used where a chain of single triangles is to be adjusted. For an extensive triangulation figure with overlapping triangles, the direction method of adjustment is preferred.

adjustment, Bowie method—A method devised by the U.S. Coast and Geodetic Survey under the direction of William Bowie for the adjustment of large networks of triangulation. A description of the method is given in USC&GS Special Publication No. 159, “The Bowie Method of Triangulation Adjustment.” (USC&GS is now known as the National Ocean Service.)

adjustment, collimation—See collimation adjustment.

adjustment, constrained—A least-squares adjustment, usually performed after a minimally constrained adjustment, using all available control. See also adjustment, minimally constrained.

adjustment, direction method—A method of adjustment of observations which determines corrections to observed directions. In the direction method, each angle is considered as the angular measure between two directions, for each of which a separate correction is determined. The direction method is used in the adjustment of triangulation figures which are composed of overlapping triangles, but for some work, where the survey consists of a chain of single triangles, the angle method of adjustment may be preferred. See also balancing a survey.

adjustment, leveling1 Determining corrections to measured elevations of, or differences of elevation between, points in a leveling network in such a way that the resulting elevations or differences are the best obtainable under the given conditions and from the measurements used. Adjustment removes those inconsistencies that result from accumulation of small random and systematic errors. However, the process of correcting measured elevations or differences for refraction, curvature of the earth, leveling-rod errors, etc., is not usually considered leveling adjustment. 2 The process of changing measured differences of orthometric elevation or two orthometric elevations to make the elevations of all bench marks consistent and independent of the misclosures of the circuits.

adjustment, minimally constrained—A least-squares adjustment which provides a meaningful solution based on a minimal number of independent constraints. Adjusting a GPS network while holding only one station fixed would be an example of a minimally constrained adjustment.

adjustment, station– See station adjustment.

adjustment, traverse– see balancing a survey.

adjustment, unconstrained– A least squares adjustment using only one point of control.

adjustment for collimation– see collimation adjustment.

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

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