1. Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
2. College of Applied Arts and Sciences, Beijing Union University, Beijing 100191, China
3. Laboratory of Urban Cultural Sensing & Computing, Beijing Union University, Beijing 100191, China
4. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
5. College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China