1. State-Province Joint Engineering Laboratory of Spatial Information Technology for High-Speed Railway Safety, Southwest Jiaotong University, Chengdu, People's Republic of China
2. Faculty of Geosciences and Engineering, Southwest Jiaotong University, Chengdu, People's Republic of China
3. Key Laboratory of Ministry of Education on Land Resources Evaluation and Monitoring in Southwest China, Sichuan Normal University, Chengdu, People's Republic of China