Once the integrity concept and the local error models are derived, the next part of the project consisted of the proof of concept (PoC).
The PoC, also called experimentation, consists of a set of different test cases to assess the performance of the proposed solution (see Test Cases post for more information). The main conclusions derived for maritime are:
Protection Levels and Availability Performance
- For ocean navigation of autonomous vessels, the required availability was met for most users. However, coastal navigation did not meet the stringent Alarm Limit of 12.5m.
- Continuity was also assessed, showing similar trends, with better results in open sky environments.
- Degraded performance due to increased masking angles and differences in multipath error and Pnlos was observed in harsh environments (port and inland waters).
Sensitivity Analysis
- The assessment of different configurations revealed that multipath mitigation techniques in GNSS receivers significantly impact ARAIM performance, with improvements in HPL values when local errors are mitigated by 20-40%.
- Exposure time and effective samples showed minimal impact on HPLs, with slight improvements in urban environments.
- Computational load analysis indicated that the number of subsets and satellites in view directly influence CPU time, with urban scenarios requiring slightly more processing time.
- Dual antenna implementation showed slight improvements in open sky scenarios and better stability in urban environments when the dual antenna was enabled.
- The number of satellites used in computation also affected ARAIM performance, with expanded constellations improving HPLs and availability.
FDE Test and Assessment of Integrity
- In open sky scenarios, the FDE is not relevant for accuracy and PL statistics.
- However, in harsh environments (port and inland waters), the PLs increase with the application of the Virtual FDE, as it leads to the rejection of more satellites. It also reduces errors and suppresses Misleading Information Events, making it an essential feature for urban environments.
- The use of FDE also reduces the maximum error value during a feared event.
Based on these findings, it is recommended to:
- Investigate an improvement that could eliminate the outliers.
- Study different approaches for implementing the effect of the dual antenna and improving the performance of the ARAIM algorithm.
- Use more than two constellations to include more satellites in the solutions and improve availability in harsh environments.
- Explore the possibility of adding hybridization with other sensors.
