1. Anhui Engineering Laboratory of Geo-information Smart Sensing and Services, Chuzhou University, Chuzhou, China
2. College of Computer Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, China
3. Key Laboratory of Virtual Geographic Environment, Nanjing Normal University, Nanjing, China
4. Department of Information Technology and Decision Sciences, Old Dominion University, Norfolk, VA, USA