1. Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, China
2. Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University, Nanjing 210023, China
3. School of Geography Science, Nanjing Normal University, Nanjing 210023, China
4. Department of Geography, University of Wisconsin, Madison, WI 53706, USA