Research On High-precision Shipborne Measurement Method Of Deflections Of The Vertical Based On GNSS/SINS Integration

Deflection of the vertical(DOV)is significant and fundamental in many applications such as geodesy,geophysics,resource exploration and high precision inertial navigation.The integration of inertial navigation system(INS)and global navigation satellite system(GNSS)can be used to measure the deflection of the vertical under dynamic conditions,and it has become a difficult and frontier topic in gravity measurement fields.A novel method for DOV dynamic measurement by using GNSS/SINS integration is proposed in this thesis based on the analysis in several key problems.The proposed method aims to improve the DOV measurement accuracy in the shipborne condition.The theoretical modeling,error budget,the statistical modeling of DOV signal,and the experimental study for evaluation of the accuracy are carried out in order to assess the feasibility of the proposed method.The main works and conclusions are as follows.(1)The error mechanism of the traditional vector gravity measurement methods using GNSS/INS integration has been analyzed,and a new DOV measurement method is proposed based on the error analysis.A theoretical analysis of the gravity-induced GPS/INS navigation attitude errors is presented.The analytic results of attitude errors caused by DOV are derived based on the inertial navigation error model.The mechanism of the coupling between GNSS/SINS attitude errors and DOV signal is also revealed.The numerical simulation is carried out to prove the theoretical results.The results indicate that the coupling between the GNSS/SINS attitude error and the DOV signal is the key problem in limiting the accuracy improvement of the traditional DOV measurement method with GNSS/SINS integration.(2)A novel DOV dynamic measurement method based on observing the GNSS/SINS attitude error has been proposed.Firstly,an attitude reference decoupled from DOV is constructed with the raw gyroscope data.Then,DOV and various systematic errors including attitude reference error and inertial sensor errors are accurately modeled.The long-wavelength components of DOV are compensated with global gravity model,and the short-wavelength components are modeled as derivative second-order Gauss-Markov processes.Finally,DOV and systematic errors are simultaneously estimated by a Kalman smoother.Due to the accurate and proper modeling,the DOV can be separated from the systematic errors.(3)The general characteristics of the high-frequency DOV disturbance's power spectrum are studied based on the global geo-potential modeling theory.The analytic relationship between the PSD of horizontal gravity disturbances along survey lines and the gravity degree error is derived according to the geo-potential theory.The power spectrums of high frequency DOV errors induced by commission and omission errors of EIGEN-6C4 model are analyzed respectively.According to the statistical analysis,some general rules for model parameters setting-up are concluded.(4)The numerical simulation is carried out to assess the feasibility of the proposed DOV measurement method.The simulation results show the GNSS noise and the accelerometer noise are important factors in influencing the DOV tracking ability of GNSS/SINS integration.The GNSS noise and the accelerometer noise will enlarge the high-frequency DOV tracking error of GNSS/SINS integration.The attitude reference error induced by gyroscope angular random walk and bias instability is the main error source of DOV measurement.The gyroscope angular random walk and bias instability will spread the PSD of attitude reference error in high-frequency region,compound the coupling effect between the attitude error and the DOV signal,and then introduce errors into the DOV measurements.The feasibility and robustness of the 2nd-order Gauss-Markov process for high-frequency DOV modeling are also investigated through simulation.(5)A ship-borne survey campaign with SINS/GNSS integration is conducted to validate the feasibility of the proposed method.The experimental results show that the internal accuracy of the four sets of DOV data can reach better than 0.3?.When the wavenumber correlation filter(WCF)algorithm is applied to the DOV results obtained by each system along the repeated lines,the DOV estimation from these two systems show good consistency,and the internal accuracy can be improved to better than 0.2?.Measurement results obtained by different systems along different survey lines are compared.The comparison results show that a system with better gyroscope bias stability can provide better DOV measurement accuracy.(6)In order to restrain the influence of DOV measurement error caused by the turning effect of the vehicle,the rotational modulating technology is applied in GNSS/SINS integration for the DOV measurement.Simulation is carried out to verify the feasibility of this strategy,and a comparison experiment between the DOV measurements of rotational INS and SINS was carried out in order to validate the accuracy improvement of the rotational INS for DOV measurement.The simulation and experimental results show that the rotational INS can improve the observability of the horizontal accelerometer bias,restrain the influence of the vehicle head maneuvering on DOV measurement results,and improve the DOV measurement accuracy.The experimental results show that the internal accuracy of the DOV measurement can reach better than 0.25?.When wavenumber correlation filter algorithm is applied,the internal accuracy can be improved to better than 0.1?...