1 School of Civil Engineering and Geomatics, Southwest Petroleum University, Chengdu, 610500, China.
2 Sichuan Water Resources and Hydroelectric Investigation & Design Institute Co.Ltd, Chengdu, 610500, China.
3 School of Civil Engineering and Geomatics, Southwest Petroleum University, Chengdu, 610500, China. xiongjn@swpu.edu.cn.
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. xiongjn@swpu.edu.cn.