Bathymetry and tidal flat topography from Sentinel-1 acquisitions

摘要

Algorithms for automatic processing of bathymetry in shelf oceans as well as the creation of topography for tidal flat areas from Sentinel-1 Synthetic Aperture Radar (SAR) satellite data were developed. SAR bathymetry processing is applicable in oceans with water depths of about 10 m to 100 m. This is a crucial depth range for many offshore construction areas like wind parks. The high costs of bathymetry generation with conventional ship surveys are a major reason for the lack of accurate bathymetry data worldwide. Using radar satellites like Sentinel-1 and automated algorithms, the effort of generating bathymetry data on suitable coasts worldwide is strongly reduced. The developed algorithm tracks changes of the lengths of long swell waves interacting with the seafloor, shortening the wave length due to the shoaling effect when waves reach shallower waters. In tidal flat areas like the Wadden Sea at the Danish, German and Dutch North Sea coast, the morphodynamics of seabed structures are significant; the soft seabed can change within days during severe storms. Data from past measurement campaigns using expensive ship soundings and airborne LIDAR scanning, deprecates quickly as the positions of islands, sandbanks or tidal inlets change. An automated algorithm was developed to retrieve the waterline from SAR images. For tidal flats of the Wadden Sea analysing time series of acquisitions at similar tidal states allows estimating rates of change as well as sediment transport and a combination of several images acquired within a short time frame at different tidal states allows estimating the topography. Acquisitions from the Sentinel-1 (S1) A/B SAR satellites cover most coasts worldwide. In contrast to optical satellites, SAR acquisitions are independent of illumination and cloud cover and reliably deliver new images.