A Method for Underwater Dynamic Gravimetry Combining Inertial Navigation System, Doppler Velocity Log, and Depth Gauge

In the underwater dynamic gravimetry, gravimetry system consists of strapdown gravimeter based on inertial navigation system (INS), Doppler velocity log (DVL), depth gauge (DG), and ultrashort baseline acoustic positioning system (USBL). Among them, INS provides the attitude and specific force; the velocity and depth are given by DVL and DG, respectively; the position is measured by USBL. However, USBL is challenged by the underwater extreme environment. We analyzed the underwater gravimetry errors and found that horizontal position errors have no great contribution to gravity calculation. Thus, a new method based on integrated navigation combining INS, DVL, and DG is proposed without USBL. To evaluate the availability of the new method, an underwater gravimetry experiment was constructed in 2018. Test results using the proposed method show that the internal accuracies of two measuring lines are 1.06 and 0.89 mGal, respectively, with a spatial resolution of about 250 m. Compared with the method based on integrated navigation combining INS, DVL, USBL, and DG, the new method can reach comparable accuracy and meet the requirement of seafloor resource exploration.