Spatially continuous dam monitoring

Terrestrial Radar Interferometry (TRI), which is based on microwave signals, can observe a large area within a short time (less than a few minutes per acquisition), along with very high precision (< 1 mm). These properties make TRI especially interesting for investigating spatially distributed, time-variable effects with low amplitudes as are e.g. vital for deformation monitoring of dams. By monitoring the entire dam, the aforementioned anomalies may be detected with higher probability as compared to a monitoring approach based on sparsely chosen points. Additionally, TRI may allow monitoring also the nearby slopes and thus assessing its stability.

However, practical application of TRI to dam monitoring beyond research is still impeded by open issues related to uncertainties in the reproducing the acquisition geometry for multi-epoch observations, geometric effects due to different setups, discrepancies between the line-of-sight (LoS) sensing and the directions of the dominant or relevant deformation processes, signal propagation effects, and atmospheric influences within the local meteorological regime.

In a first step, we are currently investigating the impact of the uncertainties of the setup geometry and possible mitigation strategies. Once we can solve the ambiguities introduced, the focus will be on the assessment of atmospheric variables and the mitigation of them. Finally, we plan to assess setup location-specific effects and propose a strategy to optimize the setup with respect to sensitivity and mitigation of detrimental effects.

In collaboration with dam owners we also investigate the benefits and challenges for areal dam monitoring based on terrestrial laser scanning (TLS), where main challenges are, again, the sufficiently accurate establishment of a common datum by point cloud registration and/or georeferencing, appropriate geometrical configuration for obtaining sufficient sensitivity, and mitigation of atmospheric effects. On the other hand, the RGB- and intensity data provided by the scanner, along with the capability to also map terrain changes at the lake side including along the edge of the lake offers highly interesting opportunities for TLS-based dam monitoring to complement established geodetic monitoring.