1. School of Geodesy and Geomatics, Wuhan University, Wuhan, China
2. State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan, China
3. School of Earth and Planetary Sciences and the Institute of Geoscience Research, Curtin University, Perth, Australia
4. Institute for Astronomical and Physical Geodesy, Technical University of Munich, Munich, Germany