Observability Analysis and Simulation of Passive Gravity Navigation System

A new simple and low cost passive navigation system can be composed of a rate azimuth inertial platform with a gravity sensor on it, a digital gravity abnormal map and a log. The system achieves the carrier’s true position by matching the gravity sensor measurements with the existing gravity maps, so the gravity field’s characteristics effects on the positioning accuracy greatly. The simplified error model of state variables and gravity observation equation of RAPINS/gravity matching integrated system are established in this paper. Based on the observability analysis theory of piece-wise constant system, the system observability matrix is established. By means of analyzing the singular of observation matrix, the influence of gravity field’s character to the navigation parameter accuracy is derived. The simulation of RAPINS/gravity matching navigation system is carried out. The results show that, with moderate precision inertial components, along the route with evident gravity anomaly and the suitable gravity gradient, the position error of this integrated system is less than one grid which equal to gravity anomaly map resolution, and platform angle error, azimuth angle error and velocity error are not big, which can ensure the underwater carrier longterm security hidden voyage achievable.