Study on direct mapping calibration method of an electronic target based on non-diffracting beam

Based on the principle of the non-diffracting beam, a new electronic target was designed for guidance of a shield machine. The system constitution and the measurement principle of attitude angles of the electronic target were discussed. Since the accurate optic center of optic system in the electronic target was difficult to find, a new calibration method was proposed. The spot center location of the incident laser of the total station in CCD fixed in the electronic target and the angle data of the total station were combined, and a mapping database was set up. During guidance of the shield machine, the actual slope angle, rolling angle and horizontal azimuth angle of the electronic target and the center of the head of shield machine were computed by the space angle of the incident laser interpolated by the actual spot center location and the angles of electronic gradienter. The experiment shows that high calibration precision is achieved by the calibration method, and high measurement precision is gained during measurement of electronic target.