Acta Geodaetica et Cartographica Sinica ›› 2017, Vol. 46 ›› Issue (10): 1262-1273.doi: 10.11947/j.AGCS.2017.20170538

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Determination of Vertical Datum Offset between the Regional and the Global Height Datum

LI Jiancheng1,2, CHU Yonghai1,2, XU Xinyu1,2   

  1. 1. School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China;
    2. Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan 430079, China
  • Received:2017-09-20 Revised:2017-09-25 Online:2017-10-20 Published:2017-10-26
  • Supported by:
    The National Key Basic Research and Development Program of China(973 Program)(No. 2013CB733301);The National Natural Science Foundation of China(No. 41210006),National Key Research and Development Plan(No. 2016YFB0501702)

Abstract: The unification of the global height datum is a key problem to be solved for geodesy after the unification of global geodetic coordination system and three-dimension spatial datum, and the basis of global spatial information sharing and exchange. In this paper, the theoretical and practical problems of vertical datum offset between the regional height datum and the global height datum are studied. Based on the classical theory of the height system in physical geodesy, the definition of the height datum vertical offset is given, and the rigorous formulas for calculating the vertical offset are derived. The formulas can be used to deduce the three methods of the height datum vertical offset determination. On that basis, the influences of different reference system and reference ellipsoid parameters on the calculation of the vertical offset are analyzed. The results show that the reference system and the ellipsoid parameter conversion are very necessary. At the same time, the height anomaly differences method needs to consider the degree zero correction caused by the inconsistency between gravity potential of the global height datum and the one computed by the model. Based on potential difference approach and the height anomaly difference method, the vertical offset between the China 1985 national height datum and the global height datum corresponding to the normal gravity potential U0 of GRS80, WGS-84 and CGCS2000 reference ellipsoidal from the 152 GPS/leveling points near the origin of Qingdao height origin and the EGM2008, EIGEN-6C4 and SGG-UGM-1 model. The regional datum is 23.1 cm lower than the global datum based on EIGEN-6C4 and WGS-84. When the Gauss-Listing geoid (mean sea surface) is selected as the global height datum, the China 1985 national height datum is 21.0 cm higher than the global height datum. The results also show that there are still large differences among the accuracies of the current gravity field models on these GPS/Levelling points around Qingdao, which will lead to big differences in estimating the vertical datum offset between the China 1985 national height datum and the global height datum with respect to different selected data sets. Therefore, the accuracy and reliability of the current global gravity field models needs to be further improved if they were used for the height datum vertical offset determination. The theoretical and practical results of this paper could be used for the realization of the unification of the regional height datum and the global height datum.

Key words: vertical datum offset, national height datum, global height datum, GPS/leveling

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