DEM generation from ERS SAR shorelines compared to airborne crosstrack InSAR DEMs in the German Bight

Coastal regions like the intertidal area of the German Bight are continuously changing their topography due to morphodynamic processes. This fact has serious impact on the German waterways, requiring a huge amount of dragging with costs of about 8×10⁷ DM per year. To investigate these morphodynamics and to reduce the costs, an up to date digital elevation model (DEM) is needed. The DEM currently used is determined by conventional vessel-mounted echo sounder measurements, which is difficult and expensive to update, especially in very shallow areas that are navigable only during extreme tides. In order to monitor morphodynamic changes and to continuously update the changes in the bottom topography, shoreline information extracted from synthetic aperture radar (SAR) images of the European remote sensing satellites (ERS-1/2) at different tidal levels are interpolated into a DEM. Therefore, the shorelines are extracted with a new developed method using a combination of wavelet and active contours. The corresponding height information is interpolated from tide gauge data. In a final step, from this height information a DEM is generated using a weighted mean interpolation in space and time. For validation purpose, the extracted shorelines and the interpolated DEM are compared to an independent. Generated DEM based on airborne crosstrack interferometric SAR images as well as on ground truth measurements. In total some 100 ERS SAR scenes from 1992 to 2000 are used to identify morphodynamical active areas in the German Bight