1. School of Earth Sciences and Spatial Information Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
2. State Key Laboratory of Public Big Data, Guizhou University, Guiyang 550025, China
3. Institute of Aerospace Information Innovation, Chinese Academy of Sciences, Beijing 100864, China
4. Faculty of Science, University of Johannesburg, Johannesburg 2006, South Africa