Application of terrestrial laser scanning methodology in geometric tolerances analysis of tunnel structures

摘要

With the point-clouds from a terrestrial laser scanner, surveying of all types of geometric tolerance has never been easier in controlling all aspects of tunnel shape and providing displacement vectors of the finished components. This paper describes how to select a suitable laser scanner, the calibration method, the procedures for acquiring survey data by the instrument in the field, and the computational algorithms of computer software needed for registration, fusion and error analysis of multimodality and range images so that the point clouds obtained by the instrument can be applied effectively in assessing the various geometric tolerances of tunnel structures in the as-built surveying. Laser scanners are chosen by surveyors based on: (a) the system's ease of use; (b) laser range and accuracy; (c) adjustable scanning speed, scan density and field of view; (d) type and class of laser; (e) weight and size of the instrument, tripod and battery; and (f) special features such as internal camera/video, weather proofing, computer hardware and software. Before being used in the field, it should be calibrated against a reference surface established by geodetic methods.