1. Institute of Ocean Engineering, Shandong University of Science and Technology, Qingdao 266590, China
2. Key Laboratory of Survey and Mapping on Island and Reef of NASMG, Qingdao 266590, China
3. College of Geomatics, Shandong University of Science and Technology, Qingdao 266590, China
4. School of Electronic Information, Wuhan University, Wuhan 430079, China