Coastline Detection Using Cross-interferometric Coherence of ERS and ENVISAT SAR images

A coastline is the boundary between land and ocean masses. Knowledge of coastline is essential for autonomous navigation, geographical exploration, coastal erosion monitoring and modeling, water line change, etc. Many methods have been researched to extract coastlines from the synthetic aperture radar (SAR) and optic images. Most methods were based on the intensity contrast between land and sea regions. However, in these methods, a coastline detection task was very difficult because of insufficient intensity contrast and the ambiguity in distinguishing coastline from other object line. In this paper, we propose an efficient method for the delineation of coastline using cross-interferometric coherence values estimated from a pair of ERS and ENVISAT images. The proposed method uses the facts that a tandem pair of ERS and ENVISAT satellites is acquired from a time interval of thirty minutes and that the coherent and incoherent values in coherence map are land and water, respectively. The coherence map was generated from a tandem pair of ERS and ENVISAT, filtered by MAP filter, and divided into land and water by the determination of threshold value that is based on the bimodality of the histogram. Finally, a coastline was detected by delineating the boundary pixels. There was a good visual match between the detected coastline and the manually contoured line. The cross- interferometric coherence map will be helpful to identify land and water regions easily, and can be used to many applications that are related with a coastline.