Vertical Angle Calibration of a Theodolite

Theodolites are one of a wide range of geodetic measuring instruments used in the geodesy, surveying and civil engineering industry. They are used to perform accurate angle measurements in both horizontal and vertical planes. Testing and calibration of these instruments is quite a complicated task, especially their vertical angles. Calibration of horizontal angles can be performed relatively easier by using angle reference standards, but these methods cannot be practically used for calibration of vertical angles. This paper will describe and investigate other practical methods for calibration of vertical angles. The first method is based on the polygon-autocollimator system. The polygon has 12 mirrors that gives 300 angle increments. The second method is based on a trigonometric angle determination.