1. Institute of Geodesy and Photogrammetry, Technische Universität Braunschweig, Braunschweig, Germany
2. School of Surveying and Geospatial Engineering, College of Engineering, University of Tehran, Tehran, Iran
3. Intelligent Robotics Research Division, ETRI, Daejeon, South Korea
4. School of Engineering, Institute for Infrastructure and Environment, University of Edinburgh, Edinburgh, U.K.