Novel method to determine laser scanner accuracy for applications in civil engineering

One of the most important aspects of controlling the condition of civil engineering structures is the deformation monitoring. 3D laser scanners show some advantages related to the controlling of unexpected deformations which cannot be monitored with total stations or levels. Technical datasheets provided by laser manufacturers give the accuracy of single point measurements, although these figures can be improved using fitting algorithms. This paper depicts a novel technical procedure used to detect real accuracy that can be achieved using surface fitting techniques. This technique is based on the displacement of an aluminum plate by means of a precision actuator. Shift produced in the plate is measured by a laser scanner and a total station. Accuracy is evaluated as the difference between the values given by the actuator and those provided for the geodetic instruments. The procedure has been tested using a laser scanner RIEGL LMS Z390i and a total station Leica TCR 1102. The results obtained are very close in both cases and depict values of accuracy less than 1 mm. These results confirm the possibilities of the RIEGL system to detect small deformations. It can be concluded that this system can be used in the monitoring of civil engineering structures. On the other hand, the single point measurement exhibits an accuracy around 6 mm and confirms the data provided by the manufacturer of the laser scanner.