抄録
Profile shape evaluation by detecting tangential angles of the profile can evaluate profiles accurately without any shape references and it has been adopted for evaluating highly accurate objects from ancient. It makes the method to be also competent for evaluating large objects. Here, we use a gyro for detecting the angles. It can evaluate profiles in a horizontal plane, which cannot be evaluated by an inclinometer. It can also evaluate profiles without being limited in its measurement range, while that of an autocollimator is limited by its measurement beam range. Fluctuations of angular signal of the gyro are eliminated by continuous reversal measurement, which is carried out by obtaining second differences of the angular signals from the continuously rotating gyro. The angle of the gyro rotating axis against the axis of the earth rotation can be derived by using two gyros rotating inversely with each other without being affected by the fluctuations.
