Accuracy in target center evaluation using Riegl LMS Z390i laser scanner and Riscan Pro software

Terrestrial laser scanners are important instruments in architecture, civil engineering, cultural heritage, mining and industry. The accuracy of the system is determined from several parameters of influence (type of laser, quality of encoders, stability of the tripod, measurement range and changes in the environmental conditions). The surveying of large objects requires a number of base stations and a registration process to obtain a point cloud in the same reference system. The registration is typically done using targets fixed on the object surface and the determination of their center is an important source of error. In this work, the accuracy in the evaluation of the center of the targets, using the scanner Riegl LMS Z390i and its software Riscan Pro, is calculated for a set of horizontal and vertical angles. Riscan software automatically detects the center of the targets using intensity based segmentation and the geometrical calculations. Comparing the coordinates obtained from the laser scanner system software and the ground truth, an increasing in the error with the decreasing of the incident angle is observed. A linear fit is used for the study of the trend and there are not important differences between the type of target (circular or square) and the type of angle (horizontal or vertical).