Tightly Coupled GPS/INS Integration for Differential Carrier Phase Navigation Systems Using Decentralized Estimation

S.E. Langel, S.M. Khanafseh, F-C. Chan, B. Pervan

Abstract:	Much research has been conducted in the area of tightly coupled GPS/INS, and this work has resulted in a vast array of navigation algorithms. A common theme of these methods is that they operate on low rate GPS ranging measurements of code and carrier phase together with high rate raw inertial measurements, such as specific force and inertial angular velocity. For stand-alone (i.e., non-differential) GPS navigation applications, high data rate INS outputs can be properly accommodated with today’s computer processors. For relative (i.e., differential) GPS navigation applications, the optimal analogous solution would be for the mobile user to have access to the reference station’s raw inertial measurements along with its own. However, due to communication bandwidth limitations, it is generally not possible to broadcast high data rate inertial navigation data. In response, an alternative tightly-coupled, differential GPS/INS navigation system is developed here using a decentralized Kalman filtering approach, which can operate at manageable broadcast data rates. The essence of the concept is that both the user and reference platforms run their own stand-alone, tightly coupled GPS/INS Kalman filter algorithms to produce estimates of position, velocity and attitude (PVA). The reference station broadcasts these state estimates at a low data rate to a differential Kalman filter onboard the user platform, which together with the corresponding usergenerated state estimates, constructs nominal values of the relative position and relative velocity states. Based on this nominal state trajectory, the filter then incorporates low rate-GPS differential code and carrier phase measurements to estimate the deviation of the true state from the nominal state. The estimation performance of the decentralized differential Kalman filtering scheme is compared to tightly coupled architectures where high rate raw inertial measurements are hypothetically available. An example application of the decentralized differential filter, an aircraft executing a figure eight flight maneuver, is specifically considered in this analysis for quantitative performance comparisons.
Published in:	Proceedings of IEEE/ION PLANS 2010 May 4 - 6, 2010 Renaissance Esmeralda Resort & Spa Indian Wells, CA
Pages:	397 - 409
Cite this article:	Langel, S.E., Khanafseh, S.M., Chan, F-C., Pervan, B., "Tightly Coupled GPS/INS Integration for Differential Carrier Phase Navigation Systems Using Decentralized Estimation," Proceedings of IEEE/ION PLANS 2010, Indian Wells, CA, May 2010, pp. 397-409. https://doi.org/10.1109/PLANS.2010.5507177
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