## 5 Results and Discussion
### Effect of Jammer on Precision  
The most interesting part of this research was the ability of the receivers to effectively calculate their position, regardless of the jammer's presence. As shown in Figure 13a (Leica GS15) and 13b (Leica GS18), the geodetic receivers generally give a better position or do not report any position at all, although the Leica GS18 can recover faster. Note, however, that the latter uses fewer satellites after recovery (Figure 13b). On the other hand, the phones continue to report their position. However, their accuracy is reduced due to the use of fewer satellites (Figure 14a), or they become confused (as in the case of Figure 14b).  
Figure 12: CNR dependence on the position of the jammer (see Figure 11 for an explanation) for various jammers (left column J1, middle column J2, and right column J3) and satellites (lines from top to bottom: C11 on B1, E10 on E1, E10 on E5a, G01 on L1, G01 on L5, and R02 on G1) as acquired by a Samsung S20. The color of the points represents the satellite elevation. The plots are provided here for a broad picture only, and the numbers might appear unreadable. For more detailed plots, please visit [[https://gsns.fpp.uni-lj.si/2022-09-19](https://gsns.fpp.uni-lj.si/2022-09-19)]([https://gsns.fpp.uni-lj.si/2022-09-19](https://gsns.fpp.uni-lj.si/2022-09-19)) (accessed on 19 February 2022).  
In terms of position-quality reporting, the phones generally give much worse results. Even if the geodetic receivers sometimes provide a wrong fix solution (Figure 13b on the right, between \(-200\) and \(-130\) m), probably due to a full period phase mismatch corresponding to the wavelength (approx. 20 cm), it is more likely that a smartphone will get a wrong fix solution (again in the same range, or its multiple) beside wrong float solutions, which are not as problematic on their own, as the end user is expecting them not to be accurate.  
It should also be mentioned that the receivers are not always the reason for a solution miscalculation. In fact, in the case of one measurement on the Huawei P40 (however, not confined to it) the software used to process the acquired data was the source of the false positioning. We preferred to use the RTKLIB for data processing, since it is open source and gives the solution quality and the number of satellites involved in the calculation. However, as can be seen from Figure 15, the calculation is completely wrong. When different software was used (Leica Infinity), the results were much closer to the real position, although still unusable for an accurate position determination. Although the differences between both below the centimeter scale were observed for all the calculations, Leica Infinity gave much better results in those few cases when the calculated position was scattered significantly. This type of behavior was observed only when the receiver was a smartphone and never on a geodetic receiver.  
Figure 13: Horizontal accuracy for geodetic devices. After the arrival of the jammer in the vicinity of the receiver they either stop reporting their position (case (**a**)—Leica GS15) or use a smaller number of satellites for the determination (case (**b**)—Leica GS18).