1. School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China
2. School of Computer Science, Hubei University of Technology, Wuhan 430068, China
3. Wuhan Tianjihang Information Technology Co., Ltd., Wuhan 430010, China
4. School of Geomatics and Urban Spatial Information, Beijing University of Civil Engineering and Architecture, Beijing 102616, China