1. Lecturer, School of Information and Control Engineering, Qingdao Univ. of Technology, Shandong 266520, China (corresponding author).
2. Master’s Student, School of Information and Control Engineering, Qingdao Univ. of Technology, Shandong 266520, China.
3. Professor, School of Information Engineering, China Univ. of Geosciences (Beijing), Beijing 10083, China.