1. School of Geographic and Biologic Information, Nanjing University of Posts and Telecommunications, Nanjing, China
2. Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing, China
3. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, China
4. College of Civil Engineering, Nanjing Forestry University, Nanjing, China