Integrated GPS, LORAN-C and INS for Land Navigation Applications

摘要

LORAN-C has long been considered as a backup system to GPS since it uses long wavelength signals that are robust to interference and operate at a very different frequency to GPS. However, the performance of LORAN-C based positioning for land applications has not been demonstrated to meet the requirements for the majority of applications. Additional non-GPS sensors are therefore needed to integrate with LORAN-C in order to improve the positioning accuracy. Applications such as land and sea navigation could make use of the improved reliability that such a system could afford. In addition, in the future when applications such as road user charging become prolific, an alternative to GPS positioning may become necessary as GPS signals are very easily jammed. This paper investigates the performance of an integrated GPS/INS/LORAN-C system. When GPS measurements are available they can be used to estimate the errors on the LORAN-C signals. In the absence of GPS signals, LORAN-C measurements can be used for long periods of time to aid inertial sensors to provide continuous positioning in all environments. The paper demonstrates that a prototype system using GPS, LORAN-C and a tactical grade INS can provide positioning performance of better than 64m in all environments, including the dense urban conditions of a large UK city. The integration algorithms are described using a Kalman filter to combine the three sensors. Future developments are also described to provide ways in which the prototype system can be potentially improved.