# Predicting C/N0 as a Key Parameter for Network RTK Integrity Prediction in Urban Environments
## 6 Conclusions  
For predicting the integrity of NRTK positioning in the framework of an optimum path planning, we need to better predict the quality of the observations. In this contribution, we investigate the prediction of the most important quality measure, i.e., the carrier-to-noise density ratio C/N\({}_{0}\). For this purpose, we use a ray-tracing algorithm combined with a 3D building model, a simple channel model to predict the signal availability, as well as attenuation due to the antenna gain pattern, diffraction effects, signal reflections or propagation through foliage. Considering the partial knowledge of the antenna gain pattern as well as shortcomings of the building model like incompleteness in needed details as well as computational intensive operations especially for investigations beyond single reflection events, the general C/N\({}_{0}\) prediction fits well the real data of the one commercial receiver compared with. Taking the typical C/N\({}_{0}\) scatter of approximately 1 dB-Hz at higher elevations into account, the obtained mean offsets of 1-3 dB-Hz for classes LOS and Multipath are in a good agreement. The time series of the predicted C/N\({}_{0}\) indicate most of the abrupt C/N\({}_{0}\) changes correctly, which coincides with a loss of the carrier phase signal and thus the absence of a reliable RTK solution.  
Further investigations will focus on the impact of predicted signal deterioration on the positioning results. To this end, a linearized Kalman Filter will be used to predict integrity parameters, i.e., position error and protection level.  
\begin{table}
\begin{tabular}{c c c c} \multicolumn{4}{c}{**Phase**} \\ \hline \multirow{4}{*}{GPS} & \multirow{2}{*}{\%} & Real & Real \\  & & Visible & Not Visible \\ \cline{1-1} \cline{2-4}  & Predicted & 59.14 & 10.47 \\ \cline{1-1} \cline{2-4}  & Predicted & & \\ \cline{1-1} \cline{2-4}  & Not Visible & 0.66 & 29.73 \\ \hline \end{tabular}
\end{table}
Table 4: Adjusted confusion matrix with the C/N\({}_{0}\) threshold of 30 dB-Hz. The green color indicates true positive and true negative, the red color indicates false positive and false negative. Numerical values are in percent only for predicted satellites.  
Figure 14: Histogram of the difference between the predicted and real C/N\({}_{0}\) values for four different visibility statuses.  
**Author Contributions:** Conceptualization and methodology, A.K. and S.S.; software, A.K.; writing--original draft preparation, A.K.; writing--review and editing, S.S. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the German Academic Exchange Service (DAAD) Graduate School Scholarship Program (GSSP) number 91750240 as part of the DFG funded research training group i.c.sens. The publication of this article was funded by the Open Access Publishing Fund of Leibniz Universitat Hannover.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Acknowledgments:** The authors would like to thank [PERSON] for providing the diffraction information. [PERSON] supported and assisted for the data acquisition.  
**Conflicts of Interest:** The authors declare no conflict of interest.