1. Lecturer, Zhengzhou Institute of Surveying and Mapping, Zhengzhou 450001, China (corresponding author).
2. Master Candidate, Zhengzhou Institute of Surveying and Mapping, Zhengzhou 450001, China.
3. Lecturer, Zhengzhou Institute of Surveying and Mapping, Zhengzhou 450001, China.
4. Professor, Zhengzhou Institute of Surveying and Mapping, Zhengzhou 450001, China.
5. Associate Professor, Zhengzhou Institute of Surveying and Mapping, Zhengzhou 450001, China.
6. Associate Professor, Changsha Univ. of Science and Technology, Changsha 410114, China.