Flood Extraction from SAR Images Based on Semi-Automatic Thresholding

A new flood extraction method which combines semi-automatic thresholding and change detection is proposed. First, a line across land and water is drawn manually. The locally optimal threshold is calculated automatically along the line from two endpoints to middle. Using this threshold, the low backscattering regions are extracted to generate a preliminary flood map. Then, the neighborhood-based change detection method combined with the entropy thresholding is adopted to detect the changed area. Finally, pixels in both the low backscattering regions and the changed regions are marked as “flood”. The effectiveness and practicality of the flood extraction method was demonstrated by a set of Sentinel-1A data and ground truth data provided by the Copernicus Emergency Management Service (EMS).