1. School of Computer Science and Engineering, Central South University, Changsha, China
2. School of Electronic Information, Central South University, Changsha, China
3. Institute of Remote Sensing and Geographic Information System, Peking University, Beijing, China
4. Department of Geomatics Engineering, Changsha University of Science and Technology, Changsha, China
5. School of Automation, Central South University, Changsha, China
6. College of Electrical and Information Engineering, Hunan University, Changsha, China