Waterline detection and monitoring in the German Wadden Sea using high resolution satellite-based radar measurements

Kurzfassung

High resolution remote sensing Synthetic Aperture Radar (SAR) data from TerraSAR-X/Tandem-X satellites are used to determine and monitor the waterline in the German Wadden Sea area. The Wadden Sea is a very unique and dynamic coastal region located in the North Sea in the German bight. Tidal flats extend several kilometres away from the coast during low tide with features like tidal inlets and sand banks. Under the influence of tidal water currents transporting large amounts of eroded material, these sand banks are also moved over time; heavy storms can even cause large variations in sand bank extensions in merely a few hours. The Wadden Sea is also subject to high ship traffic to the ports of Hamburg, Bremerhaven, Wilhemshaven and others. Hence, observation of obstacles like sand banks and decreasing water depth is crucial for maritime security. Conventional monitoring campaigns with ships or airplanes are economically expensive and can only provide limited coverage. From the high resolution TerraSAR-X/Tandem-X data of the Wadden Sea and large river estuaries like Elbe and Weser, the waterline at the time of recording is extracted using an automatic algorithm with Near-Real-Time capability. This allows for a fast and large scale determination of changes in island and coastal outlines. Additionally, the bathymetry of the observed area can be determined from the extracted waterlines by combining data from many different flybys at different tidal levels.