## 5 Simulated Jamming Results Analysis
### Low jamming Scenario
#### 5.1.2 Second Trajectory  
In this trajectory, the jamming signal was inserted between minutes 14 and 16, as in the first trajectory. Like the first trajectory, by using the GPS DF signals, or the GPS TF signals, the horizontal positioning errors exceed 8 m and 6 m, respectively, as shown in Figure 11a,b. The vertical positioning errors exceed 15 m for both GPS DF and GPS TF-based solutions, as shown in Figure 12a,b. When the Galileo SF signals are added to the GPS TF signals, the horizontal positioning errors are reduced to less than 5 m, but the vertical positioning error still has large spikes during the jamming interval. This is an indicator that adding SF signals from Galileo cannot improve the positioning solution, especially under jamming. Using the Galileo TF along with the GPS TF improves the positioning solution performance under jamming for both the horizontal and vertical positioning components. Additionally, adding the GLONASS SF signals to both the GPS TF and the Galileo TF signals improves the performance of the positioning solution. This leads to a better positioning solution, especially during jamming intervals, for the GPS TF + Galileo TF + GLONASS SF solution, with a maximum error of about 3 m and 10 m in the horizontal and vertical directions, respectively. Moreover, the GPS TF + Galileo TF + GLONASS DF-based solution shows the best performance with horizontal and vertical errors of less than 2 m and 5 m, respectively, during the jamming interval. As shown in Figure 13, the minimum number of visible satellites increased from 5 satellites using GPS TF signals to 10 satellites by adding Galileo signals and 15 satellites when adding GLONASS signals. As shown in Table 3, the performance of the GPS TF-based solution is much better than the counterpart solution from the first trajectory. However, the Max positioning errors are about 6 m and 16 m for the horizontal and vertical components of the positioning solution, respectively. Adding the Galileo SF signals does \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Combination**} & \multicolumn{3}{c}{**Horizontal**} & \multicolumn{3}{c}{**Vertical**} \\  & **RMSE** & **Mean** & **Max** & **RMSE** & **Mean** & **Max** \\ \hline GPS DF & 48.434 & 6.560 & 1141.527 & 147.512 & 13.840 & 3283.053 \\ \hline GPS TF & 3.528 & 3.482 & 8.156 & 3.964 & 2.777 & 31.026 \\ \hline GPS TF + Galileo SF & 3.294 & 3.272 & 8.187 & 2.746 & 1.980 & 23.401 \\ \hline GPS TF + Galileo TF & 2.720 & 2.678 & 4.624 & 1.766 & 1.578 & 4.624 \\ \hline GPS TF+ Galileo TF + GLONASS SF & 2.853 & 2.825 & 4.851 & 1.845 & 1.687 & 4.851 \\ \hline GPS TF + Galileo TF + GLONASS DF & 2.409 & 2.384 & 3.074 & 1.115 & 0.980 & 4.024 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: RMS error, mean, and maximum (max) positioning errors with low jamming [first trajectory]. Figure 10: Number of visible satellites for different GNSS signal combinations [first trajectory]. not improve the positioning solution compared to the GPS TF-based solution, as indicated in Figures 11 and 12. However, the root mean square error (RMSE) is improved by about 41% and 30% in the horizontal and vertical directions by using the GPS TF + Galileo TF signals, compared to using only the GPS TF signals. Additionally, the RMSE is improved by about 31% in the horizontal direction by using the GPS TF + Galileo TF + GLONASS SF signals, compared to using only the GPS TF + Galileo TF signals. However, there is unexpected positioning performance of the GPS TF + Galileo TF + GLONASS SF-based solution in the vertical direction, as shown in Figure 12a,b, leading to larger RMSE and Max errors compared to the GPS TF + Galileo TF counterpart. By using the GLONASS TF signals instead of the GLOANSS SF signals, the RMSE is improved by about 73% and 35% in the horizontal and vertical directions, respectively, compared to the GPS TF + Galileo TF-based solution.