1. School of Geographic and Biologic Information and the Health Big Data Analysis and Location Services Engineering Laboratory of Jiangsu Province, Nanjing University of Posts and Telecommunications, Nanjing, China
2. School of Geographic and Biologic Information, Nanjing University of Posts and Telecommunications, Nanjing, China
3. College of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing, China
4. Department of Geography, Geomatics and Environment, University of Toronto Mississauga, Mississauga, Canada