1. School of Geography, Nanjing Normal University, Nanjing, People’s Republic of China
2. Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing, People’s Republic of China
3. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, People’s Republic of China
4. School of Geographic and Biologic Information, Nanjing University of Posts and Telecommunications, Nanjing, People’s Republic of China