Moving base INS/GPS vector gravimetry on a land vehicle
Abstract (Summary)The Inertial Navigation System and Global Positioning System (INS/GPS) system has been extensively studied over several decades, mostly for the purpose of navigation and kinematic position. Because the INS system is affected by gravitation, the integration definitely needs gravity data in order to yield accurate results. It is natural to reverse the problem and attempt a measurement of the gravity vector. The gravimetric system based on INS/GPS shows good performances in the airborne scenarios. Moving the system into a ground vehicle will help to improve the resolution of the gravity estimates, considering its lower speed and altitude. However, the system will face much more complicated dynamics and harsh observation conditions. In this study, a two-stage extended Kalman filter based on processing noise adaptation is used to fix the position gaps and provide prior information of the Inertial Measurement Units (IMU) errors. The kinematic acceleration is computed by both the position method and the phase method. All these procedures improve the steadiness and precision of the system. The advanced wavelet de-noising technique is employed to further isolate the gravity disturbance from the observation errors in the residuals of the novel Kalman filter, previously developed at the Ohio State University (OSU). The final precision of the gravity disturbance estimates is further improved by correlatively filtering the repeated estimates in the frequency domain. An intensive survey campaign was carried out to test the validities of these techniques. Based on data analysis, the results show significant consistency (as good as 0.6mGal, STD) in the vertical component on the repeated traverses, and comparison to control data indicates an accuracy of 2-3mGal (STD). However, it is also determined that the control data, being interpolated from a database, have an accuracy of approximately 3mGal (STD). Resolution of the estimated gravity disturbance is about 2km. Large scale errors exist in the horizontal gravity estimates. Removing these on the basis of extensive deflection of the vertical control yields repeatability in the horizontal components in the range of 2-15mGal (STD) and agreement with the control at the level of 5-9mGal (STD).
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Date of Publication:01/01/2007