TABLE 1

Simulation Conditions

Navigation requirementsIntegrity requirements allocated to the IMU fault hypothesis, IIMU3.3 × 10−8 /hour = IGNSS/IMU /3 = (10−7/hour)/3 (IGNSS/IMU is equally allocated among the three hypotheses, as defined in Figure 3)

Continuity requirements allocated to the false alert event under the IMU fault hypothesis, CIMU (= Pfa,IMU*)

*Only the continuity requirement due to a false alert is considered

0.5 × 10−6 / hour = *CGNSS/IMU /2 = (10−6/hour)/2 (*CGNSS/IMU is equally allocated among the two fault monitors, as defined in Figure 3)
GNSS constellation31 GPS constellations
GNSSGNSS error model
  • -Satellite clock/ephemeris error: 2.4 m (1σ)

  • -Ionospheric error: 0 m (removed using dual-frequency measurements)

  • -Tropospheric error: WAAS tropospheric model (RTCA, 2001)

  • -Multipath error: *2.6 × WAAS airborne multipath model (RTCA, 2001)

  • *2.6 is the multipath inflation factor caused by using L1/L5 dual-frequency measurements (Walter et al., 2010)

GNSS measurement update rate2 Hz
Prior probability of GNSS faults10−5
IMUIMU error model
  • -Tactical-grade IMU noise level (Groves, 2007)

  • -Gyroscope noise (power spectral density [PSD]): 3.4 × 10−11 rad2/s

  • -Accelerometer noise PSD: 3.8 × 10−6 m2/s3

  • -Gyroscope bias PSD: 2 × 10−12 rad2/s3

  • -Accelerometer bias PSD: 1 × 10−7 m2/s5

IMU measurement update rate100 Hz
Prior probability of IMU sensor faults10−5
Flight trajectoryHovering scenario (static)
  • Note: WAAS: Wide area augmentation system.