Assessment of Time Delays and Synchronization Errors in Real-time INS/GNSS Systems and its Impact on the Navigation Performance

Heba N. Abu Abdelsalam, Mohamed M. Atia, Chris Goodall, Aboelmagd Noureldin, Naser El-Sheimy

Abstract:	In practical real-time integrated navigation systems that fuse data from Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS) [1][3][4][5] and Inertial Navigation Systems (INS) [2][5], latencies (time delays) in inertial sensors or GNSS measurements may cause significant degradation of the navigation performance. These delays could be a significant contributor and source of errors in low-cost MEMS-based inertial sensors and GNSS receivers [8][9]. This is because the processed data in a real-time system doesn’t perfectly reflect current system dynamics. Instead, it represents the system dynamics a short period of time ago. Consequently, accurate analysis and assessment of such delays are of great importance in order to compensate for their effect in real-time system designs. Thus, this work introduces a software framework for simulating, analyzing and assessing the effects of time delays on an integrated INS/GPS navigation system. This framework depends on the emulation of real-time processing of a high-quality INS/GPS integrated navigation system. By saving the exact real-time sequence of INS sensors and GPS measurements processing steps of an Extended Kalman Filter (EKF) in a loosely coupled embedded system, we were able to develop software tools that simulate different latencies in both INS and GPS to have a good sense of the effects of these latencies on the navigation performance in the lab without the need to perform too many time-consuming real-time tests. Different delays patterns were introduced and the effects of the latencies in different dynamic conditions were analyzed. Experiments on long trajectories with different GPS visibility conditions showed the efficiency of the developed tool to assess graphically and quantitatively the effect of such latencies.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	3192 - 3197
Cite this article:	Abdelsalam, Heba N. Abu, Atia, Mohamed M., Goodall, Chris, Noureldin, Aboelmagd, El-Sheimy, Naser, "Assessment of Time Delays and Synchronization Errors in Real-time INS/GNSS Systems and its Impact on the Navigation Performance," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 3192-3197.
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