Static 3D city models are well established for many applications such as architecture, urban planning, navigation, tourism, and disaster management. The recent launches of very high resolution (VHR) Synthetic Aperture Radar (SAR) Earth observation satellites, like the German TerraSAR-X, provide for the first time the possibility to derive both shape and deformation parameters of urban infrastructure on a continuous basis. The proposal “4D City” is directed towards 4D (space-time) urban infrastructure monitoring and visualization by fusion of multiple sensors: Differential Tomographic SAR (D-TomoSAR), stereo-optical images and LiDAR (Light Detection and Ranging). The different sensors complement to each other: stereo-optical data have the best visual interpretability, LiDAR provides very accurate Digital Elevation Models (DEM), and D-TomoSAR as well as the related Persistent Scatterer Interferometry (PSI) are the only methods to provide the dynamic component of buildings with up to millimeter accuracy, e.g. seasonal thermal dilation, structural deformation, or subsidence due to groundwater extraction or underground construction.
Since VHR D-TomoSAR of urban infrastructure is a new research area, the development and improvement of appropriate robust TomoSAR algorithms will be the first focus of the project. Second, data fusion for combining the strengths of different sensors will be developed both on the geodetic and the semantic levels. Finally, a particular challenge will be the user specific visualization of the 4D multi-sensor data showing the urban objects and their dynamic behavior. Visualization must handle spatially anisotropic data uncertainties and possibly incomplete dynamic information. It may also integrate some of the data fusion steps. Different levels of user expertise must be considered.
The research envisioned in this proposal will lead to a new kind of city models for monitoring and visualization of the dynamics of urban infrastructure in a very high level of detail. The change or deformation of different parts of individual buildings will be accessible for different types of users (geologists, civil engineers, decision makers, etc.) to support city monitoring and management as well as risk assessment.