1. Center for Information Geoscience, University of Electronic Science and Technology of China, Chengdu, People’s Republic of China
2. School of Resources and Environment, University of Electronic Science and Technology of China, Chengdu, People’s Republic of China
3. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, People’s Republic of China
4. Faculty of Geographical Science, Beijing Normal University, Beijing, People’s Republic of China