Design of Monitoring Geodetic Networks of Data Using the LST (Laser Scanner Terrestrial)

Abstract

This paper presents the procedures performed in the design of a geodetic monitoring network of a dam, using Terrestrial Laser Scanner (LST). The premise that the final model of the monitored three-dimensional object is generated through the concatenation of several point clouds, obtained from various observation stations, guided the definition of some criteria considered in the planning of field data collection with LST. These criteria were defined based on tests performed with the FARO FOCUS 3D 120 Laser Scanner in 9 different scenarios. The influence that some parameters, such as point cloud resolution and the distance of the LST from the object, can exert on the final monitoring result, were analyzed. Thus it was possible to propose three different hypotheses for the network, based on these criteria. In a 3D digital model of the dam of the Mauá Hydroelectric Power Plant (HPP), where the study was conducted, data samples were simulated for each of the three hypotheses. These data were used in the error propagation equations, generating the expected uncertainties for the object points of each scene. The analysis also included positional uncertainties as a function of laser beam diameter. Finally, the network that best met expectations for monitoring from the standpoint of accuracy and field data collection functionality, was selected.