1. Geomatics Section, Department of Civil Engineering, Faculty of Engineering Technology, KU Leuven, Ghent, Belgium
2. Department of Earth observation science, Faculty of Geo-information Science and Earth Observation (ITC), University of Twente, Enschede, The Netherland
3. School of Computer and Communication Engineering, Northeastern University at Qinhuangdao, Qinhuangdao, People's Republic of China