1. Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing Normal University, Nanjing, Jiangsu, China
2. College of Geographic Sciences, Nanjing Normal University, Nanjing, Jiangsu, China
3. State Key Laboratory Cultivation Base of Geographic Environment Evolution (Jiangsu Province), Nanjing, Jiangsu, China
4. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, Jiangsu, China
5. Department of Geography, University of Wisconsin−Madison, Madison, WI, USA