Establishment of Chart Datum and Vertical Datum Transformation for Hydrography in the Chinese Great Wall Bay, Antarctic Peninsula

The Great Wall bay has become an important investigation area due to the establishment of the Chinese Antarctic Great Wall scientific research station. Establishing a seamless chart datum and its transformation model with other vertical data is the key to unifying the sea-land measurement in vertical references. In view of this, two transformation models are constructed using two different realizations of the geodetic height of the mean sea surface (MSS), coupled with a seamless chart datum model of Lowest Astronomical Tide (LAT). One transformation model (Solution 1) forms MSS height by summing the modeled values of the Earth Gravitational Model 2008 (EGM2008) and averaged absolute dynamic topography based on gridded satellite altimetry products from January 2017 to April 2018. The other transformation model (Solution 2) utilizes the gridded MSS geodetic height product of DTU15, which was derived from multimission satellite altimetry from 1993 to 2015. The LAT seamless chart datum model was calculated based on the tidal constituents derived from the Atlantic Ocean 2008 model. The experiment area is located -62.350° to -62.100° S and -59.050° to -58.600°W, which includes the entire Great Wall bay, and the accuracy of Solution 1 and Solution 2 have been assessed to be 12.0 and 11.2 cm according to the error propagation law. Then, compared with the field observation result by the pressure tidal gauge in the Great Wall bay, there exists in Solution 1 and Solution 2 differences of 127.6 and 42.2 cm, respectively. This shows that Solution 2 is much better than Solution 1, although it still far exceeds the accuracy evaluation of the solutions. The reasons for this has to do with the lengths of time of realized MSSs and the poor accuracy of satellite altimetry in the coastal waters.