INS and INS/GPS Accuracy Improvement Using Autoregressive (AR) Modeling of INS Sensor Errors

Sameh Nassar, Klaus-Peter Schwarz, and Naser El-Sheimy

Abstract:	Current Inertial Navigation System (INS) error models that are used in most INS and INS/DGPS applications have some limitations, which in turn affect the overall system accuracy. One of these limitations is associated with the stochastic modeling of the INS sensor errors. For most navigation-grade IMUs (gyro drift 0.005-0.01 deg/h), a 1st order Gauss-Markov (GM) model is usually used for this purpose. This is also true for low-cost inertial systems (gyro drift 100-1000 deg/h) although sometimes a white noise process is utilized instead. Using long records of static inertial data, collected by a navigation-grade IMU, we have showed that the actual Autocorrelation Sequence (ACS) of such INS sensors is not always well represented by a 1st order GM process, where the computed ACSs have higher-order terms. The approximation of these higher-order processes by a 1st order GM process can lead to significant accuracy degradation. To overcome this problem, this paper discusses modeling INS stochastic errors using Autoregressive (AR) models of orders higher than one. Modeling inertial sensor errors using AR processes was initially tested on a limited static data set. Initial results showed that the performance of AR processes is much better than the performance of the commonly used 1st order GM process. Based on these results, AR models have been extensively tested using two INS/DGPS kinematic tests in land vehicle environment. In this paper, the actual behavior of inertial sensor errors of different categories (navigation-grade, medium-grade and low- cost) is investigated. Numerical analyses are performed to illustrate the poor accuracy of ACSs that are obtained from inertial experimental data. Finally, the AR modeling results are presented and analyzed for the case of INS stand-alone navigation and INS/DGPS positioning during frequent DGPS outage situations.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	936 - 944
Cite this article:	Nassar, Sameh, Schwarz, Klaus-Peter, El-Sheimy, Naser, "INS and INS/GPS Accuracy Improvement Using Autoregressive (AR) Modeling of INS Sensor Errors," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 936-944.
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