1. Geodetic InstituteNorwegian Mapping Authority Hønefoss Norway
2. Department of GeosciencesUniversity of Oslo Oslo Norway
3. Lantmäteriet Gävle Sweden
4. Department of GeosciencesUniversity of Hong Kong Hong Kong Hong Kong
5. State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and GeophysicsChinese Academy of Sciences Wuhan China