TLS-Defo

Roads, bridges and dams are ageing. How long will such structures be sustainable? The new research group "Deformation Analysis with Terrestrial Laser Scanner Measurements (TLS-Defo)" (spokesperson: Heiner Kuhlmann, University of Bonn) aims at taking a step forward in answering these questions.

Infrastructures, such as bridges or dams, are reaching their critical lifetime. It is estimated that about 5,000 bridges in Germany and about 50,000 dams worldwide are in a critical condition. As a result, they pose an increased risk potential, which is countered, for example, by full bridge closures as well as elaborate and expensive reconstruction measures.

Fig.: The Brucher Dam is one of the research group's test objects (Photo: IGG, University of Bonn)

The research group "TLS-Defo", funded by the German Research Foundation (DFG), aims at detecting critical behaviour of infrastructures at an early stage so that repair measures can be initiated in time. The background is that safety-critical behaviour of structures is already indicated at an early stage by small deformations. These small geometric changes, which are in the range of a few millimetres, can be detected with geodetic measurement methods.

The new research group uses terrestrial laser scanning (TLS) for this purpose: an object is scanned in a grid pattern with the help of a laser beam. By simultaneously measuring distances and angles, coordinates of the individual scanned object points are determined, resulting in a spatially highly resolved geometric description of the object. Such repeatedly acquired point clouds form the basis for the detection of geometric changes of the object. Within the framework of the research group, approaches for modelling the acquired point clouds are developed, and interpretable measures for object changes are derived by comparing these models.

Whether the detected changes are actually deformations of the object or measurement uncertainties is then statistically verified within the framework of a deformation analysis. A realistic evaluation of the changes thus requires knowledge about the complete uncertainty budget of measurements of a terrestrial laser scanner. This is one of the innovations of the research group: For the first time, a complete modelling of measurement uncertainties of the terrestrial laser scanner is carried out for use in the context of a deformation analysis.

The coordinated research work of the research group is reflected in several individual projects, each of which contributes to the overall goal. In addition to the University of Bonn (spokesperson: Heiner Kuhlmann) and the KIT, Leibniz Universität Hannover, TU Munich and TU Vienna are involved in the research group with individual projects.

For a successful start of the research group we are currently looking for several PhD students: Call for applications.