Yan Jia, Heng Yu, Quan Liu, Nanjing University of Posts and Telecommunications, China; Yan Lv, Nanjing University of Information Science and Technology, Nanjing 210044, China, China; Zhen Wu, Nanjing University of Posts and Telecommunications, China; Shuanggen Jin, School of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo 454003, China, China; Fabio Peinetti, Patrizia Savi, Politecnico di Torino, Italy