1. Department of Information Engineering; Shandong University of Science and Technology, Daizong Avenue, Taishan District, 271000 Taian; China
2. Crop Science Group, Institute of Crop Science and Resource Conservation (INRES), University of Bonn, Katzenburgweg 5, D-53115; Bonn Germany
3. State Key Laboratory of Mining Disaster Prevention and Control; Shandong University of Science and Technology; Qingdao China
4. Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A, Datun Road, Anwai 100101; Beijing China