# Galileo: The Added Value for Integrity in
## 4 Experimental Set-up  
In order to validate the proposed approach and to analyze the efficiency of the synergy between the implemented RAIM algorithm and the GPS/Galileo multi-constellation solution, static data have been used. The data were collected in the Joint Research Centre (JRC) site in Ispra, Italy. More than two hours of 1-Hz data were collected using a multi-constellation, multi-frequency receiver. The receiver was placed in a parking area between three high buildings, which reflect GNSS signals and cause severe multipath errors in the GNSS measurements. In Figure 1, the environment where the antenna was placed is shown: GNSS signals can be degraded by multipath due to the buildings surrounding the receiver. This type of environment was selected in order to demonstrate the capability of the algorithm to identify and reject multiple outliers.  
The receiver used for the test is a Javad Delta 3, which is a multi-frequency, multi-constellation high-precision device. In this study, only L1 and E1 pseudorange and pseudorange-rate measurements are considered. The Javad receiver was then connected to a geodetic multi-frequency antenna, a GrAnt GST Javad high performance antenna. The position of the antenna was carefully surveyed in order to obtain an accurate position used as a reference for the computation of the position errors. The coordinates of the antenna are reported in Table 1.  
In Figure 2, horizontal dilution of precision (HDOP) and vertical dilution of precision (VDOP) of the configurations without RAIM application are plotted as a function of time; from the figure, it emerges that the geometry conditions during the data collection were not so critical. In fact, the HDOP reaches a maximum value of 2.5 and 3.1 for GPS/Galileo and for GPS only, respectively. Only a short outage is present using only GPS, as detailed in the lower box of Figure 2. The inclusion of the Galileo measurements reduces both HDOP and VDOP, and no outages are present in the case of the multi-constellation solution.  
Four different configurations are tested: the configurations are obtained combining GPS and Galileo observations with the RAIM algorithm. Hence, the configurations are:  
\begin{table}
\begin{tabular}{c c c} \hline
**Latitude (Deg)** & **Longitude (Deg)** & **Altitude (m)** \\ \hline
45.81121 & 8.62696 & 256.466 \\ \hline \end{tabular}
\end{table}
Table 1: Coordinates of the antenna placed in a parking area at the Joint Research Centre (JRC) premises in Ispra, Italy.  
Figure 1: Environment where the antenna was placed for the static test. GNSS signals are degraded by multipath due to the buildings surrounding the receiver.  
Figure 2: Horizontal dilution of precision (HDOP) and vertical dilution of precision (VDOP) of the configurations without the receiver autonomous integrity monitoring (RAIM) application as a function of time.  
* The PVT solution computed using GPS only without RAIM (GPS noRAIM)
* The PVT solution computed using GPS and Galileo together without RAIM (GG noRAIM)
* The PVT solution computed using GPS only applying RAIM (GPS RAIM)
* The PVT solution computed using GPS and Galileo together, applying RAIM (GG RAIM).  
In order to have a fair comparison among the configurations considered, three time frames are identified:  
* All of the available epochs
* Reliable epochs, _i.e._, only epochs when the solution is declared reliable by the RAIM algorithm
* Reliable common epochs, _i.e._, the common epochs between the GPS and GPS/Galileo reliable epochs.