1. College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China
2. Shandong Branch of China National Geological Exploration Center of Building Materials Industry, Jinan 250000, China
3. China Coal Electric Co., Ltd., Beijing 101300, China
4. College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Qingdao 266590, China