Table 1 Compiled failure modes of GNSS PPP
Failure mode | Error type | Prior probability | Remarks |
|---|---|---|---|
(A) Satellite and signal | |||
Bad navigation data uploaded | Step/Ramp error | ≤1 × 10−5/h per satellite in total2 | 1. Including signal deformations, fluctuations, Non-Standard Code (NSC), code-carrier divergence, etc. 2. Conservative empirical assumption for GPS (U.S. Department of Defense 2020). |
Satellite clock jump and drift | Step/Ramp error | ||
Abnormal trajectory and attitude instability | Step/Ramp error | ||
Bad signal generated or transmitted1 | Step/Ramp error/Random noise | ||
Space vehicle malfunction | Step error/Random noise | ||
(B) Medium (Atmosphere) | |||
Ionospheric scintillation and variability | Step/Ramp error/Random noise | UI (Under Investigation) | |
Tropospheric variability | Step/Ramp error | UI | |
(C) Products (corrections) | |||
Errors in precise orbit and clock products (corrections) | Step/Ramp error | 1 × 10−6–1 × 10−5/h per satellite3 | 3. Empirical estimates of Trimble RTX (Real Time eXtended) corrections (Rodriguez-Solano et al. 2019). |
Errors in real-time ionospheric corrections | Step/Ramp error/Random noise | ∼ 1 × 10−5/h per satellite3 | |
Errors in real-time tropospheric corrections | Step/Ramp error | ∼ 1 × 10−6/h per satellite3 | |
Incorrect Earth Orientation Parameters (EOP) | Step/Ramp error | UI | Constellation-wide fault (Dıaz et al. 2014). |
Incorrect modelling of satellite antenna phase centre | Bias/Oscillation | UI | |
Incorrect modelling of receiver phase centre | Bias/Oscillation | UI | |
Incorrect code biases | Bias | UI | |
Incorrect phase biases | Bias | UI | |
(D) Work environment | |||
Code multipath | Step error/Random noise | Environment and receiver dependent | |
Code NLOS | Step error/Random noise | Environment dependent | |
Carrier-phase multipath | Random noise | Environment and receiver dependent | |
Carrier-phase NLOS | Step error/Random noise | Environment dependent | |
Unintentional interference | Step error/Random noise | Environment dependent | |
Jamming and spoofing | Step/Ramp error/Random noise | Environment dependent | |
Cycle slips | Step error | Environment dependent | |
(E) User | |||
Receiver and antenna faults | Step error/Random noise | Receiver dependent | |
High dynamics | Step error/Random noise | User dependent | Can introduce high Doppler shifts, leading to increased noise or loss of signal tracking |
Inappropriate dynamic model | Step/Ramp error | User dependent | Faults in predicted states in a Kalman filter |
Incompatibility or inconsistency | Bias/Oscillation | User dependent | |
Incorrect fixed ambiguity | Step error | Service and user dependent | |
Communications problem | Step/Ramp error | UI | |