# Galileo: The Added Value for Integrity in
## 6 Conclusions  
In this work, an effective RAIM algorithm for LBS applications has been implemented. The algorithm exploits the potential of a GPS/Galileo multi-constellation solution. An RAIM quality check for GPS/Galileo multi-constellation navigation has been considered and experimentally analyzed considering a harsh environment where a single GNSS may not satisfy minimum navigation requirements in terms of availability, continuity, accuracy and integrity. The parameters adopted to evaluate the performance of the algorithm in terms of accuracy were the SD, maximum and mean errors. The parameters were computed for both horizontal and vertical components of the position and velocity solutions.  
In order to evaluate the performance in terms of availability, two different parameters were adopted depending on the application or not of RAIM techniques. Specifically, the SA is used when the RAIM algorithm is not applied, and the RA is introduced when quality checking is performed. In order to assess the performance of the configurations considered, a static test has been carried out: data were collected in a parking area between three high buildings, which reflect GNSS signals, causing severe multipath errors in the GNSS measurements. Hence, the assumption of a single blunder within the measurement set is not realistic. For this reason, quality checking has been performed iteratively, rejecting observations until no additional outliers are identified or until the solution is declared impossible to check. The classical FB algorithm has been modified, introducing a preliminary check to verify the robustness of the satellite geometry and a separability check to avoid erroneous rejection. The algorithm has been further modified considering different weights for GPS and Galileo observables.  
From the analysis, it emerges that GPS alone is not able to provide accurate and continuous navigation in signal-degraded environments. Although the introduction of RAIM improves the performance of GPS-only navigation, the solution availability is significantly reduced. This availability  
Figure 22: CDFs of the vertical position errors when a classical RAIM approach is considered. Upper box: CDFs computed using all available epochs; central box: CDFs computed using only reliable epochs; lower box: CDFs computed using only reliable common epochs.  
reduction is compensated by the inclusion of Galileo measurements, which enhance performance with respect to the baseline configuration. The inclusion of Galileo measurements alone may not be sufficient for achieving the required level of performance, since also the multi-constellation solution is characterized by large errors. The joint adoption of Galileo and RAIM improves performance with respect to the baseline configurations for all of the considered parameters: horizontal error parameters are more than halved with respect to configurations without RAIM. Furthermore, the vertical errors are significantly reduced.  
The performance of the proposed algorithm is compared with respect to the performance of the classical RAIM algorithm: the proposed approach provides improvements in terms of maximum and mean errors for both horizontal and vertical components.  
In the velocity domain, the benefits of the Galileo inclusion are less evident: the combined use of Galileo observables and RAIM algorithms improves the performance mainly in terms of maximum errors, which are strongly reduced in both horizontal and vertical components.  
Finally, the performance of the proposed algorithm is compared to that obtained using the classical FB algorithm: the benefits of the proposed modification clearly emerge. The proposed algorithm provides improvements for all of the considered parameters.  
With this in mind, the synergy between multi-constellation solutions and RAIM can be a key element for enabling LBSs in signal-degraded environments.