Procedure to evaluate the accuracy of laser-scanning systems using a linear precision electro-mechanical actuator

Deformation monitoring is critical for the inspection of civil engineering structures. Three-dimensional laser-scanning systems can provide the ability to control unexpected deformations that cannot be monitored with traditional topographic instruments, such as total stations or levels. Technical data sheets provided by laser manufacturers typically give the accuracy of single-point measurements, but these specifications can be improved using surface-fitting of the data points. In this study, a procedure is used to detect the true accuracy that can be achieved using surface-fitting techniques. The procedure uses a precision actuator that moves an aluminium plate whose shift can be measured by the geodetic instrumentation. Accuracy is calculated as the difference between the values given by the actuator and the values from the geodetic instruments. The procedure is tested using a laser scanner, Riegl LMS Z390i and a total station, Leica TCR 1102. Similar results are obtained in both cases and accuracies are less than 1 mm. The results confirm that this Riegl system can be used to detect small deformations and can be applied to monitor civil engineering structures. The single point measurements confirm the data provided by the laser scanner manufacturer with an accuracy of approximately 6 mm.