Gravity disturbance influence analysis and compensation on high-precision INS in polar region

Considering the requirement of vessel navigation capability in polar region, the influence of gravity disturbance on high precision inertial navigation system and the compensation method of gravity disturbance are studied. Firstly the projection of gravity disturbance in the transversal geographic coordinate system is deduced. Furthermore, the horizontal gravity disturbance is modeled as a deterministic constant and a Markov process respectively, and the influence of gravity disturbance on transversal strapdown INS is analyzed. EIGEN-6C4 is used to obtain polar gravity disturbance data, and the data is interpolated by cubic spline interpolation method. Based on the polar gravity disturbance data, the error induced by gravity disturbance in a transversal strapdown INS is compensated. The theoretical analysis and simulation test results demonstrate that constant horizontal gravity disturbance will introduce oscillation error and constant bias into inertial navigation system in transversal geographic coordinate system. On the other hand, the horizontal gravity disturbance will lead to linear oscillation growth in the position error, and the drift rate of position error is related to variance of gravity disturbance, velocity of vessel and order of Markov process, which is consistent with the error caused by conventional coordinates. After gravity disturbance compensation based on the EIGEN-6C4 gravity field spherical harmonic model expanded to 2190 order, the accuracy of pitch angle and roll angle is improved by 68%, and the positioning accuracy is improved by 2.5%. © 2022, Editorial Department of Journal of Chinese Inertial Technology. All right reserved.