  This paper develops, implements, and validates a powerful single-antenna
carrier-phase-based test to detect Global Navigation Satellite Systems (GNSS)
spoofing attacks on ground vehicles equipped with a low-cost inertial
measurement unit (IMU). Increasingly-automated ground vehicles require precise
positioning that is resilient to unusual natural or accidental events and
secure against deliberate attack. This paper's spoofing detection technique
capitalizes on the carrier-phase fixed-ambiguity residual cost produced by a
well-calibrated carrier-phase-differential GNSS (CDGNSS) estimator that is
tightly coupled with a low-cost IMU. The carrier-phase fixed-ambiguity residual
cost is sensitive at the sub-centimeter-level to discrepancies between measured
carrier phase values and the values predicted by prior measurements and by the
dynamics model, which is based on IMU measurements and on vehicle constraints.
Such discrepancies will arise in a spoofing attack due to the attacker's
practical inability to predict the centimeter-amplitude vehicle movement caused
by roadway irregularities. The effectiveness of the developed spoofing
detection method is evaluated with data captured by a vehicle-mounted sensor
suite in Austin, Texas. The dataset includes both consumer- and
industrial-grade IMU data and a diverse set of multipath environments (open
sky, shallow urban, and deep urban). Artificial worst-case spoofing attacks
injected into the dataset are detected within two seconds.
