Cancelation and Monitoring of GNSS Spoofing Using Loose INS Coupling

GNSS is prone to jamming and spoofing, which should therefore be handled to avoid PNT errors. In this work, we propose a GNSS spoofing cancelation algorithm in a loosely INS coupled navigation filter. The proposed algorithm is based on detection of the spoofing attack, using filter innovation within a time interval, followed by determination of a point in time to recompute the navigation filter to avoid spoofing data inclusion and filter uncertainty due to rapid movements. With these algorithm attributes the same decision for detecting spoofing can be reused for deciding when a spoofing attack has ended, since more realistic covariance estimates and smaller error should be achieved even for late detected spoofing attacks. We show by simulation that the proposed algorithm perform well in relevant spoofing scenarios. It is shown that recomputation of the filter from an earlier timestep is crucial to be able to determine when the attack ends. By re-computation with INS only, and excluding GNSS when the motion is rapidly changing and when spoofing is present, slower growing errors and more realistic covariance estimates are achieved.