An algorithm for optimizing terrestrial laser scanning in tunnels

This article describes a new method for planning terrestrial laser scanning (TLS) measurements in tunnels that determines the optimal positions of the scanner throughout the tunnel. The method is implemented in an algorithm that automatically establishes the minimum number of scanner positions and their relative positions, while assuring the fulfillment of a set of quality restrictions for the point cloud. The quality requirements are based on the study of the incidence angle expected for the laser beam on the tunnel surface, the distance to the sensor and the point density. The algorithm works in tunnels with straight or curved axes whose cross-sections can be approximated by circular and/or elliptical arcs.