# Predicting C/N0 as a Key Parameter for Network RTK Integrity Prediction in Urban Environments
## 5 Prediction Results  
### C/N\({}_{0}\) Prediction  
In Figures 12 and 13, the predicted C/N\({}_{0}\), as well as the measured ones, are depicted for six different GPS PRNs. In each of the C/N\({}_{0}\) time series, the color code at the bottom shows the solution status (cf. Figure 2), and the color code around 10 indicates the status of the signal as expressed in Figure 6. Furthermore, tree intersection, the possibility that the signal be reflected more than once, and the tracking status of the phase signal in the receiver are also included in this bar.  
Figure 12a shows the results for PRN 3 which has an azimuth of \(-100^{\circ}\) and an elevation of \(74^{\circ}\) (cf. Figure 12d). For this PRN, the trees are correctly detected before C and after J, and the corresponding attenuation is calculated. As it is quite high-elevated, it is generally in an LOS condition with some diffraction parts which are correctly aligned with  
Figure 11: Flowchart summarizing the steps to predict C/N\({}_{0}\).  
Figure 10: Real position of one of the trees (**right** and **middle**) and the 3D model used to predict the signal fading by the foliage (**left**).  
measured data. Figure 12b shows the results for PRN 4 with an azimuth of \(-170^{\circ}\) and an elevation of \(23^{\circ}\) (cf. Figure 12d). It is obstructed in many parts of the trajectory. In some blocked areas, diffraction is predicted which seems realistic, e.g., between points I and J. While in some cases, e.g., between G and H, it is predicted as blocked, and also no phase is tracked, there are some low C/N\({}_{0}\) values. After point J, a dense block of trees, obscures the signal completely. In addition, the spike at point K can be attributed to a tree. Figure 12c depicts the predicted and measured C/N\({}_{0}\) for PRN 17 which has an azimuth of \(-68^{\circ}\) and an elevation of \(44^{\circ}\) (cf. Figure 12d). The overall level of predicted values is in the range of measured values, especially in LOS situations. The simulation correctly shows no decrease in C/N\({}_{0}\) for foliage before point C, while other spikes because of trees, are well detected and evaluated. The decrease after point D up to before F is simulated by the NLOS status, but the level of the signal is significantly decreased up to 15 dB-Hz, whereas simulation shows a decrease of maximum 5 dB-Hz. At the point of drop, being tagged by diffraction, a decrease of 13 dB-Hz can be seen. Exactly at the point of C/N\({}_{0}\) drop, the phase signal is interrupted.  
Figure 13a depicts the results for PRN 19 with an azimuth of \(-45^{\circ}\) and an elevation of \(26^{\circ}\) (cf. Figure 13d). This PRN is tracked in a blocked area in the diffraction mode between B and C. Here, also a sudden decrease in C/N\({}_{0}\) stops phase tracking. Between F and G, some consecutive trees make teeth shape, and another tree is detected just before G, where the attenuation is predicted much lower than the real data. In continue, some spikes after H, after I, at J and K, are well detected as trees, but the values are not completely aligned with real data or slightly displaced. This could be due to the limited accuracy of the tree models. Figure 13b shows predicted and measured C/N\({}_{0}\) for PRN 22 which has an azimuth of \(75^{\circ}\) and an elevation of \(81^{\circ}\) (cf. Figure 12d). This PRN has a high elevation, and the phase signal istracked continuously. Figure 13c illustrates C/N\({}_{0}\) results for PRN 32 with azimuth and elevation of \(44^{\circ}\) and \(18^{\circ}\), respectively (cf. Figure 12d). PRN 32 has a low elevation and is rarely in an LOS situation. After points D to F and also between G and H, the code is tracked that could be from multi-reflection. The phase signal is only partly tracked, mainly in LOS situations. Some spikes after K, are well detected because of foliage.