A Novel Eötvös Correction Method Based on Passive Velocity Compensated INS

The significant challenge faced by underwater gravity matching navigation is the precise acquisition of velocity information for real-time Eötvös correction of marine gravimeters without emitting or receiving external signals. To address this issue, we propose a passive velocity compensation method for inertial navigation systems (INSs), which can effectively enhance the velocity measurement and positioning accuracy of the INS in a completely passive state and calculate high-precision Eötvös correction. This method takes into account the impact of horizontal gravity disturbance on the velocity measurement of the INS, utilizes the Earth's gravity field model and satellite altimetry technology to construct a high-precision horizontal gravity disturbance reference map, and uses the information in the map for velocity compensation. Relative to the INS without compensation, it achieves higher precision in velocity and positioning, which can be served in real-time for the Eötvös correction of marine gravimeters. To verify the new method, we equipped a high-precision INS and a marine gravimeter to conduct marine dynamic experiments in the South China Sea. The experimental results show 1) the new velocity compensation method can reduce the average velocity error of the INS by 33.3% in a completely passive state; 2) integrating the velocity results after compensation can obtain higher positioning accuracy than before compensation, with an average reduction of 13.3% in location error; and 3) the passive velocity compensation method, compared with the pure INS, reduces the standard deviation of the Eötvös correction error of the marine gravimeter by 27.0%, which can better serve in many important application fields, including underwater gravity matching navigation.