1. School of Geography and Information Engineering, National Engineering Research Center for Geographic Information System, China Univ. of Geosciences, Wuhan 430078, China.
2. Faculty of Architecture, Univ. of Hong Kong, Hong Kong 999077, China.
3. School of Geography and Information Engineering, National Engineering Research Center for Geographic Information System, China Univ. of Geosciences, Wuhan 430078, China (corresponding author).