Research On High Accuracy Integrated Navigation In Underwater Gravimetry

The resolution of shipborne gravimetry is limited due to the water between the measurement site and source of the gravity anomalies.If dive to the near-bottom area or even to the bottom,it would significantly improve the resolution and strengthen the signal,obtaining more abundant gravity information.This is underwater gravimetry technologies,which is in a starting experiment stage.When it is compared with traditional shipborne gravimetry,there are many advantages.Thus,it is of high value to research on underwater gravimetry.High accuracy integrated navigation technology is a key point in underwater gravimetry.It is essential to select appropriate underwater acoustic navigation instruments to take the place of GNSS in integrated navigation system because there is no GNSS signal in the water.However,there are still many sophisticated problems to be solved due to the absence of GNSS signal.DVL and USBL are selected in this paper to take the place of GNSS to build underwater integrated navigation system with SINS gravimeter.The study focuses on how to use these two instruments complete SINS dynamic alignment and DVL calibration,with no GNSS signal.The main contents and work include the following aspects:(1)The principle and the error model of DVL and USBL are briefly introduced.And the error model of SINS/DVL as well as the error model of SINS/USBL is constructed.(2)Researching on SINS dynamic alignment in underwater gravimetry,a method of SINS dynamic alignment with assistant information of DVL velocity/USBL position has been put forward.Compared to the method of SINS dynamic alignment with assistant information of DVL velocity,the convergence speed of the former is faster the latter,with a higher accuracy.(3)Researching on underwater DVL calibration,a method of DVL calibration with assistant information of USBL position has been advanced.It can completed DVL calibration under the water with no GNSS signal.The calibration result can effectively improve the positioning accuracy of SINS/DVL underwater integrated navigation system.(4)A pro-experiment of underwater gravimetry,in which the methods of SINS dynamic alignment and DVL calibration brought forward above had been verified,was carried out.It can be concluded that SINS/DVL integrated navigation system with assistant of USBL position information have the ability to align in dynamic environment and calibrate DVL.The results are accurate and reliable,which can obviously improve the accuracy of underwater integrated navigation system.