# Analysis of the Impact of Multipath on Galileo System Measurements
## 5 Discussion  
The impact of the multipath effect on code and phase observations as well as on precise positioning accuracy for the Galileo and GPS systems has been analyzed in depth in this paper. The research was based on CMC observations as well as on a short length baseline measurement. Using time-frequency analysis, the multipath error was classified due to the impact of diffuse and specular reflections. The analyses performed present the characteristics of the multipath error and measurement noise for observations made by reference GNSS stations. The results obtained confirm the theoretical assumptions that Galileo code observations are more resistant to the multipath impact compared to non-upgraded GPS signals. It was observed that the impact of both the multipath effect and measurement noise is closely related to satellite elevation above the horizon (the lower the satellite elevation, the higher the observation error). For the lowest satellite elevations, one can expect average code multipath errors (STD) ranging from 20 to 25 cm for most of the analyzed signals. The smallest values of the multipath error (approximately 13 cm), were obtained for the E5 AltROC Galileo observation, which is a 30% improvement in terms of the properties of this signal with respect to other observations of this system. The highest values of the multipath error (STD = 40 cm) were obtained for the L2W GPS observation. Galileo observations offer 13% better resistance to the multipath effect compared to GPS observations, with the exception of the E5 and L2W signals. Galileo's supremacy has also been demonstrated for observations at the basic system frequencies: E1/L1. On the other hand, individual \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**0–3 mHz**} & \multicolumn{2}{c}{**3–20 mHz**} & \multicolumn{2}{c}{**0–20 mHz**} \\ \cline{2-7}  & **Galileo** & **GPS** & **Galileo** & **GPS** & **Galileo** & **GPS** \\ \hline
**max [mm]** & \(-2.7\) & \(-0.2\) & \(-5.1\) & \(-3.1\) & \(-2.4\) & \(1.8\) \\ \hline
**min [mm]** & \(-20.4\) & \(-14.9\) & \(-14.9\) & \(-10.9\) & \(-23.7\) & \(-14.7\) \\ \hline
**range [mm]** & \(17.7\) & \(14.7\) & \(9.9\) & \(7.8\) & \(21.3\) & \(16.5\) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Maximum multipath error for vertical component measurements determined from decomposition of the signal. Figure 15: Vertical component signal extraction using wavelets for (**a**) specular, (**b**) diffuse, and (**c**) specular and diffuse multipaths. maximum observation errors related to the multipath impact can reach peak-to-peak amplitude values exceeding 1 m, as determined using the wavelet transform. In this case, the supremacy of Galileo E1 observation turns out to be even greater. Depending on the type of reflections analyzed, the peak-to-peak amplitude for the C/A GPS code is larger by at least 16% and up to as much as 40%. The STD of measurement noise of the code observations ranges from 2 cm for E5 Galileo to 25 cm for L2C GPS for the lowest satellite elevation range. Even when not taking into account the AltBOC signal, the remaining Galileo observations have a reduction characterized by reduced measurement noise by almost 40% compared to GPS observations. The multipath impact on the undifferentiated phase observations for the lowest satellite elevations was recorded at the level between 2 and 3.5 mm. This impact is closely related to the carrier wavelength of a given signal. The phase observation noise was determined at the level of 1 to 2 mm. For high satellite elevations, it is approximately 0.5 mm. The maximum multipath impact on DD phase residuals can reach values with a peak-to-peak amplitude as high as 20 mm. Since similar measurement conditions for both GNSS systems were ensured, the positioning accuracy for the positioning model used in this paper is very similar for both systems. The inferiority of the still much less available Galileo system has been demonstrated only for the determination of the vertical component.