1. Ph.D. Candidate, Dept. of Surveying and Geo-Informatics, Tongji Univ., Shanghai 200092, China.
2. Associate Professor, Dept. of Surveying and Geo-Informatics, Tongji Univ., Shanghai 200092, China (corresponding author).
3. Professor, Dept. of Surveying and Geo-Informatics, Tongji Univ., Shanghai 200092, China.