1. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing, China
2. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
3. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application and School of Geography, Nanjing Normal University, Nanjing, Jiangsu, China
4. Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing, China
5. Department of Geography, University of Wisconsin-Madison, Madison, WI, USA