Table 1.
IMO accuracy requirements for GNSS positioning (IMO, 2002)
| Navigation phase | Horizontal accuracy (m) | Integrity | ||
|---|---|---|---|---|
| Alert limit (m) | Time to alarm (seconds) | Integrity risk (per 3 h) | ||
| Ocean | 10 | 25 | 10 | 10−5 |
| Coastal | 10 | 25 | 10 | 10−5 |
| Port approach | 10 | 25 | 10 | 10−5 |
| Inland waterways | 10 | 25 | 10 | 10−5 |
| Track control | 10 | 25 | 10 | 10−5 |
| In port navigation | 1 | 2.5 | 10 | 10−5 |
| Automatic docking | 0.1 | 0.25 | 10 | 10−5 |
Figure 1.
Vessel trajectory
Figure 2.
Number of tracked satellites (left) and PDOP values (right)
Table 2.
Processing parameters for both PPP and differential solutions
| Parameter | PPP solution | Differential solution | |
|---|---|---|---|
| Dual frequency | Triple frequency | ||
| GNSS system | G, E, C | G, E, C | G |
| Observations | Code and phase | Code and phase | Code and phase |
| Mathematical model | Undifferenced ionosphere-free | Undifferenced ionosphere-free | Differenced |
| Frequency |
|
| L1/L2 |
| Sampling rate | 1 Hz | 1 Hz | 1 Hz |
| Elevation mask | 10° | 10° | 10° |
| Orbit and clock | CNES (RT) | CNES (RT) | IGS (final) |
| Tropospheric model | Saastamoinen model | ||
| Mapping function | Vienna mapping function 1 (VMF-1) | ||
| Parameter estimation | Kalman filter | ||
Figure 3.
Positioning errors in longitude, latitude, and altitude, respectively, for dual-frequency real-time PPP solutions
Figure 4.
Positioning errors in longitude, latitude, and altitude, respectively, for triple-frequency real-time PPP solutions
Figure 5.
Distribution of the differences between the dual-frequency PPP solutions and the differential solution in the three components
Figure 6.
Distribution of the differences between the triple-frequency PPP solutions and the differential solution in the three components
Figure 7.
STD of the PPP solutions in the three positioning components
Figure 8.
STD of the 2D position for the proposed PPP solutions