Accuracy requirement for altimetry observations for bathymetry inversion using gravity anomaly and gravity gradients

The gravity anomaly and vertical gravity gradient obtained from satellite altimetry observations play a great role in global bathymetry inversion. In order to design next generation of altimetry satellites for bathymetry inversion, the altimetry accuracy requirements should be first known. In this study, formulas expressing the accuracy requirements for altimetry observations for bathymetry inversion are firstly derived, and then a quantization factor K is used to directly compare the performance of gravity anomaly and vertical gravity gradient. Numerical results show that an accuracy of 100 m in bathymetry inversion with resolution higher than 10′ requires that the accuracy of altimetry-derived geoid should be better than 2 cm whether based on gravity anomaly or gravity gradient. It was also found that when the traditional altimetry satellite data is used to retrieve the bathymetry, the performance of vertical gravity gradient data is better than that of gravity anomaly in shallow water and short-wavelength region, whereas the gravity anomaly data perform better in deep water and long-wavelength region. In general, the vertical gravity gradients perform better than gravity anomaly in wavelength range of 0 ~ 12.9 km. This study can provide a reference for the design of next generation of altimetry satellites for bathymetry inversion. Also, the findings can help investigators select appropriate data for bathymetry inversion for different ocean regions.