1. School of Geography, Nanjing Normal University, Nanjing, Jiangsu Province, China
2. Key Laboratory of Virtual Geographic Environment (Nanjing Normal University), Ministry of Education, Nanjing, Jiangsu Province, China
3. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, Jiangsu Province, China
4. Department of Geoinformatics – Z_GIS, University of Salzburg, Salzburg, Austria