Evaluation of the geopotential value W 0 LVD of China

Estimation of the zero-height geopotential value W 0 LVD for the CVD (China Vertical Datum) plays a fundamental role in the connection of traditional height reference systems into a global height system. Estimation the W 0 LVD of China is based on the computation of the mean geopotential offset between the value W 0 = 62636856.0 m 2 s −2 , selected as reference in this study, and the unknown geopotential value W 0 LVD . This estimation is based on the combination of ellipsoidal heights, levelled heights (referring to the CVD), and some physical parameters, such as geopotential values, gravity values, and geoid undulations. The geoid undulations derived from the GGM (Global Geopotential Models). This combination is performed through three approaches: The first one is based on the theory of Molodensky, and the second one compares levelled heights and geopotential values derived from the GGMs, while the third one analyses the differences between GPS/Levelling and GGMs geoid undulations. The approaches are evaluated at 65 benchmarks (BMs) covered around Qingdao where the tide gauge is used to observe the local mean sea level of China. The results from three approaches are very similar. Furthermore, the W 0 LVD determined for the China local vertical datum was 62636852.9462 m 2 s −2 , indicates a bias of about 3.0538 m 2 /s −2 compared to the conventional value of 62636856.0 m 2 s −2 .