What indicators would alert you to a GNSS spoofing attempt in an integrated navigation system?

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Multiple Choice

What indicators would alert you to a GNSS spoofing attempt in an integrated navigation system?

When GNSS signals are spoofed, the most informative clues come from how the GNSS data and the inertial navigation solution disagree or fail to behave as a coherent whole. The best indicators are: - Sudden, inconsistent satellite measurements: you’d see abrupt changes in pseudorange values, unusual jumpiness in the measured ranges, or rapid loss and reacquisition of satellites that doesn’t match the actual vehicle motion or the expected satellite geometry. - Incompatible carrier-phase and pseudorange behavior: under normal operation these observables track the same physics of distance to satellites, with their evolution staying self-consistent. If spoofed signals are introduced, the phase and range data can diverge in ways the receiver cannot reconcile, producing phase ambiguities or cycle slips that don’t align with the observed motion. - Abrupt GNSS velocity or attitude changes: the GNSS solution might suddenly swing or flip when the spoofed data dominates, while the inertial measurement unit (IMU) would typically show much smoother, gradual motion. - Integrity flag anomalies: the system’s integrity monitoring (like health flags or fault-detection logic) would detect inconsistent or implausible GNSS measurements and raise alarms. Context helps: integrated navigation blends GNSS with IMU data, so contradictory GNSS outputs compared with the IMU-generated trajectory make the fusion suspect. Doppler can be degraded too by spoofing, so assuming it’s always reliable isn’t safe. Carrier-phase measurements can be spoofed as well, so they aren’t inherently immune. And spoofing is detectable by these coherence and integrity checks, not undetectable as some choices imply.

When GNSS signals are spoofed, the most informative clues come from how the GNSS data and the inertial navigation solution disagree or fail to behave as a coherent whole. The best indicators are:

  • Sudden, inconsistent satellite measurements: you’d see abrupt changes in pseudorange values, unusual jumpiness in the measured ranges, or rapid loss and reacquisition of satellites that doesn’t match the actual vehicle motion or the expected satellite geometry.

  • Incompatible carrier-phase and pseudorange behavior: under normal operation these observables track the same physics of distance to satellites, with their evolution staying self-consistent. If spoofed signals are introduced, the phase and range data can diverge in ways the receiver cannot reconcile, producing phase ambiguities or cycle slips that don’t align with the observed motion.

  • Abrupt GNSS velocity or attitude changes: the GNSS solution might suddenly swing or flip when the spoofed data dominates, while the inertial measurement unit (IMU) would typically show much smoother, gradual motion.

  • Integrity flag anomalies: the system’s integrity monitoring (like health flags or fault-detection logic) would detect inconsistent or implausible GNSS measurements and raise alarms.

Context helps: integrated navigation blends GNSS with IMU data, so contradictory GNSS outputs compared with the IMU-generated trajectory make the fusion suspect. Doppler can be degraded too by spoofing, so assuming it’s always reliable isn’t safe. Carrier-phase measurements can be spoofed as well, so they aren’t inherently immune. And spoofing is detectable by these coherence and integrity checks, not undetectable as some choices imply.

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