1. Professor, School of Geodesy and Geomatics, Wuhan Univ., Wuhan 430079, China.
2. Ph.D. Candidate, School of Geodesy and Geomatics, Wuhan Univ., Wuhan 430079, China (corresponding author).
3. Lecturer, School of Geodesy and Geomatics, Wuhan Univ., Wuhan 430079, China.