1. Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, People’s Republic of China
2. Institute of Geodesy and Geoinformation, University of Bonn, Bonn, Germany
3. Faculty of Civil Engineering, Southwest Jiaotong University, Chengdu, People’s Republic of China
4. Department of Natural Resources of Sichuan Province, Sichuan Institute of Land Science and Technology, Chengdu, People’s Republic of China