1. Faculty of Geomatics, Lanzhou Jiaotong University, Lanzhou, People's Republic of China
2. National-Local Joint Engineering Research Center of Technologies and Applications for National Geographic State Monitoring, Faculty of Geomatics, Lanzhou Jiaotong University, Lanzhou, People's Republic of China
3. Gansu Provincial Engineering Laboratory for National Geographic State Monitoring, Lanzhou, People's Republic of China