Four operational SAR-based water and flood detection approaches: a comparison

Abstract

The German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) has gained a lot of experience in surface water extraction from Synthetic Aperture Radar (SAR) data for various application domains within the last years. In this context four operational approaches have been developed which jointly form the so called DFD Water Suite: The Water Mask Processor (WaMaPro) (Huth et al. 2015, Kuenzer et al. 2013a, 2013b) bases on a simple and high-performance algorithm integrated in a license-free tool, which processes multi-sensor SAR data in order to provide decision makers with information about the location and extent of water surfaces. The Rapid Mapping of Flooding tool (RaMaFlood) (Martinis et al. 2009, 2011) is developed for semi-automatic flood extent mapping using an interactive object-based classification algorithm which is used within flood rapid mapping activities of DLR`s Center for Satellite Based Crisis Information (ZKI). The TerraSAR-X Flood Service (TFS) (Martinis et al. 2015) is used for near-real time rapid mapping activities and provides satellite-derived information about the flood extent in order to support emergency management authorities and decision makers without interaction of an active image interpreter. It bases on a fully-automated processing chain. The last approach is the TanDEM-X Water Indication Mask processor (TDX WAM) (Wendleder et al. 2013). It is part of the processing chain for the generation of the seamless, accurate and high resolution global Digital Elevation Model (DEM) and bases on data of the TanDEM-X mission by combining SAR amplitude and bistatic coherence information. Its purpose is to support the subsequent DEM editing process by the generation of a global reference water mask. In this study, the design of the four approaches and their methodological background are explained in detail, while simultaneously elaborating on the preferred application domains for the different algorithms. The advantages and disadvantages of the four approaches are identified by qualitatively as well as quantitatively evaluating the water masks derived from co-registered single-look slant range complex (CoSSC) data of the TanDEM-X mission for five test sites located in Vietnam, China, Germany, Mali, and the Netherlands (figures 1-5).