CIVIL ENGINEERING 365 ALL ABOUT CIVIL ENGINEERING



AbstractSea surface height (SSH), a measurement widely used in marine science, can be used to compute the marine gravity field while providing underlying information on the ocean current, tide, and geoid. A traditional SSH measurement relies on tide stations and satellite altimetry. Shipborne SSH measurements not only alleviate the influence of poor nearshore waveforms on satellite altimetry reliability but also enable large-scale surveys. Moreover, it is favored by the high sampling rate and superior spatial resolution. Precise point positioning (PPP) allows operations independent of the land-based station, facilitating flexibility and efficiency. Accordingly, PPP is used to determine the ellipsoid height based on shipborne GPS data. The PPP computations are performed using the Canadian Spatial Reference System (CSRS)–PPP, GrafNav, and Bernese. The results of the CSRS-PPP have better accuracy and are easy to use. The corrections of the height difference between a GPS antenna and sea surface, earth tide, ocean tide, and filtering are tested to obtain an accurate SSH measurement. The corrected SSH accuracy is improved from 206.2 to 22.9 cm based on a crossover analysis. Through the adjustment of the crossover differences, the result shows an accuracy of 7.5 cm. The comparison with the DTU18 mean sea surface (MSS) model shows that the standard deviation of the differences is 21.9 and 11.9 cm for the corrected SSH before and after the adjustment, respectively. The adjusted SSH shows an obvious improvement of 62.2% and 32.8% in the standard deviation of the crossover differences and the differences with the DTU18 MSS model.



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