Theory And Methodology Of Bathymetry Inversion Using The Oceanic Gravity Data

High precision bathymetry map is very important in shipping trade, biological research, disaster warning, geological exploration and other fields. Altimetry gravity data can reflect the seafloor topography information within a certain band, based on this, we focused on the bathymetry inversion theory and method by altimetry gravity data. The main works and creations are as the following:1、The marine gravity field inversion method based on satellite altimetry data is overviewed, the inverse Vening-Meinesz formula is used to calculate the gravity anomalies in South China Sea region,the accuracy of whom is equal to the DTU10 GRAV model; By using the shipborne data, the vertical gravity gradiant anomailes based on the geoid, gravity anomalies, vertical deviation and spherical harmonic function model are analyzed and compared.2、Taken a certain area of the South Pacific as a research object, the accuracy of the widely used ETOPO1, DTU10 BAT, GEBCO, GINA and SIO models are analyzed and assessed, the accuracy of the longwave length bathymetry models show that some models exist more serious systemic deviation.3、In gravity geologic method, the density difference constant between the oceanic crust and seawater need to be determined, the check points iterative calculation method is proposed to determine the constant, which effectively improves the accuracy of the bathymetry model.4 、 The correlation formula between the bathymetry and gravity data is given,the uncompensated admittance model, Airy compensation admittance model and deflection compensation admittance model are comparativly analyzed, studies show that the admittance method is suitable for the 15-200 km wavelength bathymetry inversion, the low-pass and high-pass filter are given to eliminate the high frequency noise impacts.5、The Smith and Sandwell(SAS) method is used to inverse bathymetry, the scale factors are obstained by anti-dropout linear regression technique in 15-120 km wavelength; The formula of SAS method based on the vertical gravity gradient anomalies is also given,in 20-200 km wavelength,scale factors are obstained by discrete shipborne data, the short wavelength bathymetry is calculated by the residual short-term depths,which improves the accuracy of the bathymetry model.6、The formula of least squares method is given to inverse bathymetry model,the transform function is fitted by the ten-order polynomial formula, this method is based on the random nature of gravity anomalies and bathymetry,so a priori high precision bathymetry model is required.7、The practical flowchart and the concrete solution step of varies bathymetry inversion methods are given. Take the Magellan seamount chain and the South China Sea as research objects, the research areas are divided according to the shipborne data distributions and terrain conditions, the accuracy of the models, power spectral density, the inversion effects of different depths, relative accuracy in shipborne points, the distribution of big error points are deeply analyzed, which indicate that the relative precision of bathymetry models in test areas are better than 6%.8、The robust parameter adjustment method is proposed to obstain the integrated bathymetry model. This method gives small weights to poor quality models, which reduce their contributions to the integrated model and improve the model’s accuracy.