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 UAVs are:
Protection Levels and Availability Performance
- The proposed long-term evolution provides a clear improvement over the short-term evolution. The implementation of 4 constellations allows for a good number of satellites to be visible even in urban scenarios.
- The improved accuracy and integrity monitoring provide high availability of service in both open sky and semi-urban scenarios.
- When considering the most difficult environments in urban flights, the availability cannot be met globally, although there seems to be room for improvement, as many regions do have acceptable availability of service.
- Depending on the actual implementation of the Kalman filter, performance could be improved, which is further investigated in the sensitivity analysis.
Sensitivity Analysis
- Achieving the required availability in all UAV operational scenarios necessitates maintaining a very low residual error due to multipath and non-line-of-sight.
- Tighter prior fault probabilities have minimal impact in urban settings; thus, efforts should focus on bounding the local user error to sub-meter levels.
- The use of masking angles and restrictions on user dynamics can ensure the integrity of the position solution within urban air mobility bounds.
FDE Test and Assessment of Integrity
- In the total of processed flights, the FDE and architecture of the evolution provided a means to detect outliers and protect against multipath and other severe GNSS errors.
- The integrity requirements are met, especially considering that the initial convergence period and its accompanying inflated protection levels can be managed through flight procedures.
- Furthermore, a simulated feared event in the form of a pseudorange ramp is demonstrated to be captured by the system while still achieving the required performance.
Based on these findings, it is recommended to:
- Conduct further sensitivity analysis using real flight data with a coupled PPP-IMU bank of Kalman filters.
- Extend research towards defining ‘corridors’ and present findings to various stakeholders, such as EUROCAE working groups, to help create suitable corridors that consider all perspectives.
