*wei li^1,2,3,4, zhao hai meng^5,6, hao wen yan^1,2,3 (1.Faculty of Geomatics, Lanzhou Jiaotong University, Lanzhou 730070, China, 2.National-Local Joint Engineering Research Center of Technologies and Applications for National Geographic State Monitoring, Lanzhou 730070, China, 3.Gansu Provincial Engineering Laboratory for National Geographic State Monitoring, Lanzhou 730070, China, 4.School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China, 5.Tianjin Navigation Instrument Research Institute, Tianjin 300131,China, 6.Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100083, China)