1. College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China
2. Department of Geosciences and Geography, University of Helsinki, 00014 Helsinki, Finland
3. College of Tourism and Urban-Rural Planning, Chengdu University of Technology, Chengdu 610059, China
4. School of Architecture and Civil Engineering, Chengdu University, Chengdu 610106, China
5. State Key Laboratory for Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China