The paper presents the application of the geodetic metrology methods to measurement of flatness of front surface of portal crane collar. The collar has a diameter of 4.500 m and it is welded on front surface of column 9.000 m high. In order to measure the flatness trigonometric method with raised accuracy was applied. The vertical and horizontal directions as well as the distances for points located on front surface collar were mea-sured with one measuring position. Total Station TC 2002 (Leica Company) and especially designed sight shield (notification to Polish Patent Office) were used in tests. Obtained measurement accuracy (0.07 mm) has allowed to evaluating the accuracy of execution of tested collar, which should be contained in interval of tolerance (0.2 mm). Almost all of points were contained in assumed interval of tolerance. The applied measurement method with boosters is useful to this type of measurements characterized by very high accuracy.

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