Detecting the Topographic Changes of Spatial Features from Sar Satellite Images Based on the Multilayer Level Set Approach

The areas covered by a river play an important role in analyzing the causes of debris flows. The damage caused by debris flows costs over a thousand million dollars in Taiwan. Usually, after natural disasters like typhoons and earthquakes have occurred, the topographic conditions are changed. How to locate these topographic changes is an important research issue for protecting people from natural disaster-related damages. Remote sensing is an efficient way to study topographic conditions occurring before and after in areas affected by natural disasters. Synthetic aperture radar (SAR) provides a remote sensing technique for exploring the ground truth in imaged areas in day and night. The interpretations of SAR images play an important part in analyzing the characteristics of the imaged areas. However, the effects of speckle signals make the interpretation of SAR satellite images difficult. Mumford and Shah proposed dividing an image into a set of homogeneous sub-regions, such that the energy contained in the image can be minimized. Based on this minimization of the energy, the multilayer level set method implicitly presents the regional boundaries as several nested level lines. By increasing the number of iterations and preselected level values, these lines evolve close to the level boundaries based on the energy minimization. The research results demonstrate that the proposed algorithm can be used to analyze given SAR images, and that the analyzed results can provide an important clue in studying the behavior of debris flows.