1. School of Environment and Spatial Informatics, China University of Mining and Technology, Xuzhou 221116, China
2. Jiangsu Xuhuai Regional Institute of Agricultural Science, Xuzhou 221131, China
3. School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China
4. School of Mathematics and Statistics, Jiangsu Normal University, Xuzhou 221116, China
5. School of Computing and Mathematics, College of Science and Engineering, University of Derby, Kedleston Road, Derby DE22 1GB, UK