Research of automatic extraction of water Bodies on ETM+images

Water bodies extraction approaches have always been the focus and hotspot in remote sensing study and application.The threshold method,such as the spectral structure method,the modified normalized difference water index method and the classification extraction method are used to extract water bodies on Landsat-7 ETM+imagery.The study indicates that the spectral structure has advan-tage of removing shadow noise,and built-up land noise is removed by using the threshold method.Satisfying results are achieved by the combination of two methods and good threshold.However,the threshold is difficult to select.Automatic extraction of water bodies method is proposed based on clustering analysis segmentation.The comparison of those methods shows that combination of spectral structure and threshold method achieves an excellent result,and automatic extraction method extracts water bodies accurately without selecting threshold value.