An Analysis of the Effect of Gravity Anomaly to Height Estimation in High-Precision INS/GNSS Integrated Navigation Systems

In this paper, we focus on how gravity anomaly affects height estimation in the high-precision inertial navigation system (INS) and global navigation satellite system (GNSS) integration. The theoretical analysis based on INS error propagation equations shows that the height error is related to gravity anomaly directly. In addition, the height-related elements in the Kalman gain matrix can be used as an indicator to evaluate the extent of the effect to height estimation. Different precision grade INSs integrated with GNSS, and GNSS of different positioning accuracy integrated with high-precision INS is simulated to analyze the effect of gravity anomaly. The simulation results show that the effect can be ignored in low-precision INS cases, while is more significant in high-precision cases, which agrees well with the former theoretical analysis. At last, a shipborne test is conducted and the experimental results show that the maximum height error of high-precision INS/GNSS integration can reach to 0.5 m if the gravity anomaly is not compensated, while can fall below than 0.1 m after gravity anomaly compensation or modeling. It shows that the existence of gravity anomaly along the track can degrade the vertical positioning accuracy of high-precision INS/GNSS integration, and should be considered in such cases.