Ableitung der Topographie des Wattenmeeres aus ERS-SAR Daten

Abstract

Aim of this thesis is the development of an operationally applicable method to derive the topography of the German Tidal Flat Area (Wadden Sea) by evaluation of satellite image using the so-called waterline method.Accurate and up-to-date topographic maps of the tidal flatsare an important basis for the protection of theWadden Sea as well as for coastal preservation.Due to the high variability of the topography in this area causedby storms and tidal currents conventionally generated maps (e.g. by echo sounding) often do not represent the actual terrain.The waterline method provides an additional approach.Here, a series of satellite images of the German Bight taken at different water levels are analysed to detect theborderline between tidal flats and adjacent water areas.After geo-coding, those waterlines are combined with the corresponding water levels to represent the topography on an irregularly spaced grid. Interpolation of these data yields a topographic mapof the intertidal zone. In this thesis the waterline method is used to map the wadden areas of Nordfriesland and Cuxhaven.The study is based on the analysis of 71 images taken by the Synthetic Aperture Radar (SAR) aboard the European Remote Sensing Satellite ERS-2 in the period from 1996 to 1999.Using a wavelet-based edge detection algorithm a largely automated estimation of the waterline is possible in spite of the high level of multiplicative noise in the SAR images. The developed procedure reduces the amount of work for an human operator considerably. A modified pass point correction is used for the geo-coding of the derived waterlines. Water levels obtained by the water level modell ofthe German Maritime and Hydrographic Agency(BSH) are assigned to the geo-coded waterlines. The resulting grid of topographic points is interpolated into a topographic map ofthe intertidal area for each of the four years using the software package TASH developed at the University of Hannover, Germany.