Page 37 - 卫星导航2021年第1-2合期

Du et al. Satell Navig (2021) 2:3 Page 4 of 22

Table 1 Compiled failure modes of GNSS PPP
Failure mode Error type Prior probability Remarks
(A) Satellite and signal
−5
Bad navigation data uploaded Step/Ramp error ≤1 × 10 /h per satellite in total 2 1. Including signal deformations, fuc‑
tuations, Non‑Standard Code (NSC),
Satellite clock jump and drift Step/Ramp error
code‑carrier divergence, etc.
Abnormal trajectory and attitude Step/Ramp error 2. Conservative empirical assump‑
instability tion for GPS (U.S. Department of
Bad signal generated or transmitted 1 Step/Ramp error/Random Defense 2020).
noise
Space vehicle malfunction Step error/Random noise
(B) Medium (Atmosphere)
Ionospheric scintillation and vari‑ Step/Ramp error/Random UI (Under Investigation)
ability noise
Tropospheric variability Step/Ramp error UI
(C) Products (corrections)
−6
−5
Errors in precise orbit and clock prod‑ Step/Ramp error 1 × 10 –1 × 10 /h per satellite 3 3. Empirical estimates of Trimble RTX
ucts (corrections) (Real Time eXtended) corrections
−5
Errors in real‑time ionospheric cor‑ Step/Ramp error/Random ∼ 1 × 10 /h per satellite 3 (Rodriguez‑Solano et al. 2019).
rections noise
−6
Errors in real‑time tropospheric cor‑ Step/Ramp error ∼ 1 × 10 /h per satellite 3
rections
Incorrect Earth Orientation Param‑ Step/Ramp error UI Constellation‑wide fault (Dıaz et al.
eters (EOP) 2014).
Incorrect modelling of satellite Bias/Oscillation UI
antenna phase centre
Incorrect modelling of receiver phase Bias/Oscillation UI
centre
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 spoofng Step/Ramp error/Random Environment dependent
noise
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
flter
Incompatibility or inconsistency Bias/Oscillation User dependent
Incorrect fxed ambiguity Step error Service and user dependent
Communications problem Step/Ramp error UI

to allocate risks using a fault tree diagram (European tree based on the FMEA analysis in section Failure
GNSS Agency 2015; Hexagon Positioning Intelligence modes and efects analysis (FMEA), modifed after
2019). Figure 1 shows an example of an integrity fault (Hexagon Positioning Intelligence 2019).