1. School of Mathematics and Computer Sciences, Nanchang University, 330031 Nanchang, China
2. State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, 430079 Wuhan, China
3. School of Safety Science and Emergency Management, Wuhan University of Technology, 430079 Wuhan, China
4. Institute of Remote Sensing and GIS, Peking University, 100871 Beijing, China