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UDC: 528.521:528.11
DOI: 10.14438/gn.2014.20
submitted: 2014-10-09, accepted: 2014-10-27, published: 2014-10-31

Determination of geodetic instruments centring error

Žarko Nestorović1*

1Powerplant Đerdap, Serbia

Abstract. Geodetic instruments, during the measurements, shall be centred properly in order to obtain the right value of measured directions, horizontal angles, zenith angles or distances. This problem is well analysed in literature for cases when it is applied in trigonometric networks. Those cases are of interest when some directions are not visible and enough number of needed measurements could be obtained. In the case of problems where the high precision of the geodetic measurements is needed the only acceptable method for centring is forced centring of the geodetic instruments and signals i.e. prisms or different kind of marks. Because of imperfections in production of tribrachs it could be expected that some eccentricity will appear in the same tribrach. There exists many ways for investigate this problem but in this paper I will present the case of investigating one tripod with one geodetic instrument. The method for centring error determination was based on the determination of coordinates of the geodetic instrument after each its movement. First group of the measurements were performed after centring the instrument on the industrial tripod and only releasing and tightening of the screw on the tribrach. Another group of measurements were performed only after centring of the instrument while the tripod was not moved i.e. with presumption that the tripod was stable. The short lines of sight were used because of expectations that small centring error could be detected.

Keywords. short lines of sight, statistical analysis, statistical hypothesis testing, normal distribution, gross-errors detecting

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