1. Institute of Artificial Intelligence, Guangzhou University, Guangzhou, China
2. Department of Engineering and Engineering Technology College of Aerospace, Computing, Engineering, and Design (ACED), Metropolitan State University of Denver, Denver, CO, USA
3. School of Information, North China University of Technology, Beijing, China
4. Department of Surveying and Geoinformatics, Nanjing University of Posts and Telecommunications, Nanjing, China
5. Department of Electronics and Telecommunications, Politecnico di Torino, Turin, Italy