# Evaluating the Vulnerability of Several Geodetic GNSS Receivers under Chirp Signal L1/E1 Jamming
## 5 Data Analysis, Results and Discussion
### Positioning Results  
The results from both the static and kinematic jamming tests showed that the jammer affected the measurements of the specific receivers differently. Furthermore, GLONASS signals from some receivers  
Figure 8: Variations of an average of C/N\({}_{0}\) on a Leica GS15 due to the passage of the jammer and its sensitivity to satellite selection within hemispheres of varying azimuths: (**a**) elevations above 10\({}^{\circ}\) and (**b**) above 40\({}^{\circ}\) (own study). Figure 9: Sensitivity of the distance related cost function on satellite selection by azimuth at a minimum elevation of 35\({}^{\circ}\), and the time shift of C/N\({}_{0}\) vs. the closest distance jammer-receiver for Leica GS15 during the last test at 90 km/h (own study). were more resistant to jamming. This can likely be attributed to the higher operating frequencies and different frequencies of GLONASS satellites. The oldest receiver used in this study, Trimble 4000 SSi, was a GPS-only receiver, manufactured in the mid-1990s. The authors deliberately investigated its performance to investigate the benefits of the new receivers. While jamming in the vicinity of the receiver at a distance of about 10 metres twice in succession, unlike other instruments, it did not detect the end of the disruption so quickly, thus there were missing observations for a period of six minutes (see Figure 10(a)). Based on its age, it performed surprisingly well in the other jamming scenarios. When comparing newer instruments, it could be said that the L1/E1 jammer also significantly influenced the acceptance of GLONASS signals, especially in the case of Trimble R8, Leica GS07 and Leica GS15. Meanwhile, Trimble R8, both of [PERSON]'s receivers and the latest Leica GS18 instrument performed much better regarding GLONASS reception (see Appendix A). The performance of the instruments was then evaluated according to their ability to calculate their position and the discrepancy of the solution from the exact value (Figure 10). The grey region shows the time interval where an instrument was unable to give any kind of solution. The green and blue circles represent the horizontal and vertical discrepancy in the case when a phase solution was given. The magenta and yellow circles represent those events when an instrument was able to get a code solution only. It should be stressed that most of the code solutions (and some phase solutions) fell outside the plotting region (up to 5 cm), because their error was typically far beyond that value (the region of interest for geodesy). It seems that the receiver most affected in the static jamming scenario was Trimble R10, which did not provide its position for more than 40 min, although the jamming took significantly less time (see Figure 10c, in detail in Figure 11). The positioning failed immediately after the first static jamming in the vicinity of the receiver (point J1 at Figure 5) and performed well when final static jamming was performed again at point J1. This is not necessarily a bad property, since for end users it is better to get no results than to get bad ones. The other receivers had significantly shorter blackouts (the grey region in Figures 10 and 11). In particular, the two [PERSON]'s instruments were able to give some solution (at least a code one) throughout the jamming campaign. It should be also stressed that most of the code solutions and some carrier-phase solutions are not seen in those graphs from Figure 10 due to the plotting scale. The latter indeed happened to another Trimble instrument, namely R8s (see Figure 12), around 09:47 UTC (87 min from 08:20). At the beginning, it was unable to get a phase fix and reported the code solution instead. Then suddenly (at 09:47), it jumped to a wrong phase fix and stayed there for approximately two minutes. Thereafter, it alternated between a wrong phase fix and the code solution for a minute. In the next minute it reported the correct phase solution, then finally reported the widelane solution, and after a minute, stopped reporting.