1. School of Spatial Informatics and Geomatics Engineering, Anhui University of Science and Technology, Huainan 232001, China
2. Xinjiang Academy of Surveying and Mapping, Urumqi 830002, China
3. School of Geomatics and Urban Spatial Informatics, Beijing University of Civil Engineering and Architecture, Beijing 100044, China
4. Chinese Academy of Surveying and Mapping, Beijing 100830, China