WATER EXTRACTION ON THE HYPERSPECTRAL IMAGES OF GAOFEN-5 SATELLITE USING SPECTRAL INDICES

Abstract. Water extraction from remote sensing images can be applied in water resources monitoring, as well as an essential preprocessing for water quality parameter retrieval. China’s new generation Gaofen-5 satellite carries a hyperspectral imager named AHSI, which is suitable for water quality monitoring. In this paper, to determine the spectral index most suitable for AHSI data’s water extraction, we selected a large lake and a reservoir in China as the study areas, and used corresponding AHSI data for water extraction experiment. In the experiment, NDWI, MNDWI and AWEI were all tested on the AHSI reflectance data, and major water bodies were delineated by implementing the histogram bimodal method on the water index images. Based on analyses with water index images and water extraction results, NDWI is shown to be the optimal index for water extraction of AHSI data among these three widely-used indexes, as it can accurately extract water bodies and also eliminate pixels of water plants or shadows between land and water. In addition, MNDWI can be used on AHSI data since it is most robust in terms of providing a bimodal histogram. AWEI is, however, not suggested to be used for water extraction of the AHSI data.