Importance

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Abstract

To obtain an accurate survey value even if a centering operation is simplified without using a specific target. When a survey point S is displayed on the screen of a display 20 as an image picked up by a CCD camera 38 in a process to perform an operation for placing a surveying instrument 10 directly above the survey point S, a centering operation is ended, and the survey point S is specified as a true centering point. Accordingly, coordinates (Xs, Ys) of the survey point S in which the instrument center point 0 is defined as an origin are calculated as a decentering amount (i.e., dislocation) of the survey point S with respect to an instrument center point 0. At this time, a horizontal angle .theta.'h determined when a target T is collimated on the basis of the instrument center is obtained by performing angle measurement, and a horizontal-angle correction amount .DELTA..theta.h is calculated on the basis of the coordinates (Xk, Yk) of the virtual centering point K and on the basis of the coordinates (Xs, Ys) of the survey point S. The horizontal angle .theta.'h is corrected by this horizontal-angle correction amount .DELTA..theta.h, and the horizontal angle .theta.h based on the survey point S is obtained.

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First Claim