1. Research Institute of Highway Ministry of Transport,Beijing,China,100088
2. Chinese Academy of Macroeconomic Research,Institute of Spatial Planning & Regional Economy (ISPRE),Beiijing,China,100038
3. Renmin University of China,School of Environment and Natural Resources,Beijing,China,100872
4. Renmin University of China,Center for Spatial Information, School of Environment and Natural Resources,Beijing,China,100872