1. College of Public Administration, Huazhong Agricultural University, Wuhan, Hubei , China
2. The State Key Laboratory of Information Engineering in Surveying, Mapping, and Remote Sensing, Wuhan University, Wuhan, 430079 Hubei , China
3. Center for Information and Communication Technology, Fondazione Bruno Kessler, Trento, 38100, Italy
4. School of Remote Sensing and Information Engineering, Wuhan University, Wuhan, China
5. Faculty of Electrical and Computer Engineering, University of Iceland, Reykjavik, IS-107, Iceland