1. State Key Laboratory of CAD&CG, Zhejiang University, Hangzhou, China
2. Wuhan Geomatics Institute, Wuhan, China
3. LIESMARS, Wuhan University, Wuhan, China
4. Finnish Geospatial Research Institute, Kirkkonummi, Masala, Finland
5. Faculty of Geo-Information Science and Earth Observation, University of Twente, Enschede, The Netherlands