1. Department of Geography & the Environment, University of Denver, Denver, USA
2. Department of Geography, University of Wisconsin-Madison, Madison, USA
3. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, China
4. Key Laboratory of Virtual Geographic Environment, Nanjing Normal University, Nanjing, China
5. State Key Laboratory Cultivation Base of Geographical Environment Evolution, Nanjing, China
6. State Key Laboratory of Resources and Environmental Information System, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China