# Evaluating GNSS Receiver Resilience: A Study on Simulation Environment Repeatability
## 5 Results  
The results of the GNSS receivers' responses to interference, in terms of position determination, can be displayed in various ways, with the events being most easily visualized using the display in Figure 7. Graphs a and b depict the U-blox 10-Series, while c and d show the U-blox 6-Series. Each graph displays all 50 measurement repetitions at once, with the red dot representing the reference position generated by the GNSS simulator software and replayed with the RF generator. The blue curve illustrates the post-processed position deviation (angular minutes for latitude and longitude). This deviation was calculated by comparing the GNSS receivers' output to a known, simulated location (used by the RF generator), not directly computed by the receiver itself. While the static display in Figure 7 reveals the magnitude of positional errors, it fails to capture the dynamic temporal response of the receiver, particularly its reaction to disturbances relative to its prior state. To address this, Figure 8 presents the results plotted against a time axis. The positional deviation was calculated as the magnitude of the vector between the true position and the receiver's reported position, representing the overall deviation without separate latitude and longitude components. A larger magnitude indicates a greater deviation from the reference. Positive values signify a north-east movement, and negative values a south-west movement from a true position. The graphs depict changes in centimeters relative to the initial stable state (the first 100 s) before any disturbances occurred, ensuring that all graphs start near \(\Delta\) 0 cm. This effectively isolates the receiver's dynamic response to disturbances by removing any fixed offset in the location's center (as can be seen in Figure 3). Each of the 50 measurement repetitions is shown as a distinct colored curve, intentionally plotted together to highlight the complexity of interpreting the results and the substantial variability in the receiver's behavior under jamming. Figure 8a, a reference measurement without jamming, illustrates the baseline performance. As an older generation receiver (U-blox NEO-6M) relying solely on the GPS L1 signal, it exhibits minor positional fluctuations over time, but these remain within the expected 1 m accuracy range. In stark contrast, the introduction of a broadband FM jamming signal, indicated by the red shaded area for 100 s, drastically alters the receiver's behavior. Initially, the receiver shows minimal response to the relatively weak jamming. However, after 50 s, the effects become pronounced, manifesting as significant positioning errors. Notably, the severity of these errors varies considerably across repetitions. While some measurements show only moderate deviations over time, others exhibit substantial shifts, frequently exceeding 2 m and, in some instances, reaching 4 m. Using the same receiver as in Figure 8, Figure 9 illustrates its response to single (a) and triple (b) CW interference at \(-\)70 dBm. With single-frequency interference, most repetitions show an immediate and substantial deviation from the true location, exceeding 10 m. The receiver's internal mechanisms then work to mitigate the interference, gradually restoring positioning accuracy to within \(\pm\)1 m. Triple-frequency interference, however, leads to a persistent inability to fully mitigate, resulting in continuous location fluctuations seen across all repetitions. While the errors diminish after the 100 s interference period, the receiver does not fully regain its initial location accuracy, a phenomenon more pronounced than in other interference modes. Figure 7: The figure presents the positional accuracy of two GNSS receivers, U-blox MAX-M10 (10-Series) and U-blox NEO-6M (6-Series), showing their deviation from the simulated position (red dot) in angular minutes of latitude and longitude.