1. Department of Geography and Planning, University of Liverpool, Liverpool, UK
2. Beijing Key Laboratory for Remote Sensing of Environment and Digital Cities, Faculty of Geographical Science, Beijing Normal University, Beijing, China
3. Department of Geography & Geographic Information Science, University of Illinois at Urbana-Champaign, Urbana, USA
4. School of Policy Studies, University of Bristol, Bristol, UK
5. College of Urban and Environmental Sciences, Peking University, Beijing, China