摘要: With the increasing multi-satellite altimetry data sets of unprecedented accuracy and spatial resolution, the marine geoid could be improved substantially. In the meanwhile, the traditional gravimetric measurements, e.g., terrestrial, shipboard and airborne gravity observations, could also be used to further improve the accuracy of the regional geoid. This paper focuses on the role of satellite altimetry in geoid determination as well as the proper combination of multi satellite altimetry data sets and heterogeneous gravity observations for regional geoid refinement. Based on the remove-compute-restore methodology, the residual disturbing potential is parameterized by using Poisson wavelets radial basis functions (RBFs). Meanwhile, the long and short-wavelength part of the gravity field is represented by global gravity model (GGM) and residual terrain model (RTM), respectively. To choose the proper functional model of satellite altimetry data, different observations derived from sea surface height (SSH), i.e., along-track deflection of vertical (DOV) and difference of geoidal height (DGH) are evaluated for their performances in regional geoid modeling. Numerical experiments show that using along-track DGH as satellite altimetry observations derives a better geoid model, the accuracy of which is improved by 0.34 cm, 0.27 cm, 1.4 cm and 2.3 cm in Netherlands, Belgium, England and relevant marine regions, respectively. The main reason is that we use geoid slope to compute DOV, which may introduce large approximation errors that propagate into regional geoid modeling. Thus, we suggest using DGH as satellite altimetry observations.
As the quality of global tide model is doubtful in shallow water areas, it may introduce errors to satellite altimetry-derived observations. In order to find the proper tide model for data preprocessing and investigate the effect on the geoid caused by the choice of the tide models, a global tide model called GOT4. 7 and regional tide model named DCSM are used in geoid modeling, respectively. Together with heterogeneous gravity data, DGH derived from global and regional tide model are used for two geoid computation, respectively. The difference between geoid based on different tide models is at a mm level, which concentrates in shallow water and specific open sea areas. The evaluation of two geoids show the effect on geoid introduced by different tide models may be negligible as the accuracy of geoid obtained from DCSM is only improved by mm level. However, a regional tide model with high accuracy is always preferable for reducing the relevant errors in satellite altimetry data pre-processing.
Moreover, the role of satellite altimetry and shipboard gravity data in marine geoid determination is studied. The result shows these two data sets are complementary with each other. Numerical experiments show the best result can be derived when satellite altimetry and shipboard data together with the other two data sets are combined for geoid modeling, the accuracy of which is 1.39 cm, 2.81 cm, 4.12 cm and 5.43 cm in Netherlands, Belgium, England and relevant marine regions, respectively. While the accuracy of geoid is decreased to 1.99 cm, 3.22 cm, 4.42 cm and 8.09 cm in the corresponding regions, respectively if the geoid is modeled without satellite altimetry data set. Similarly, the accuracy of geoid is also decreased without incorporating shipboard gravity data, which reduces to 2.15 cm, 3.61 cm, 5.46 cm and 8.15 cm over these regions, respectively. Thus, we suggest to combine satellite altimetry and shipboard gravity data set in marine gravity field determination.
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