# Loosely Coupled GNSS and UWB with INS Integration for Indoor/Outdoor Pedestrian Navigation +
## 6 Results  
To verify the accuracy of the proposed algorithm in performing seamless navigation estimation of pedestrians, we conducted several experiments consisting in a user walking along a random path from the outdoor terrace to the indoor laboratory. The user walked for a short period outside the laboratory and therefore outside the geofence area. This allows also the behavior of the algorithm in no-line-of-sight (NLOS) conditions to be analyzed and with fewer anchors to observe. In fact, the environment has a significant impact on the accuracy of measurements and consequently on the accuracy of the positioning, therefore the real time estimation was performed outdoors, indoors inside the network of UWB, and in a narrow corridor with no LOS anchors. In total, five different acquisition and real-time processing tests were made during the measurement campaign with the aim to evaluate also the reliability of the methodology. The proposed estimation algorithm based on GNSS and UWB data has provided 5 different positioning solution which were compared with the trajectory obtained with the total stations and of which the positioning error along the vertical component, in 2D and in 3D was calculated. Figure 9 shows the obtained 2D trajectory in cartographic coordinates superimposed on the orthoimage from the \"Agenzia per le Erogazioni in Agricoltura\" AGEA 2018 (pixel resolution \(30\times 30\) cm) for Test n\({}^{\circ}\) 1, where it is possible to notice the outdoor terrace and the indoor lab. Figure 10 shows the same trajectory in local reference frame in a plot grid of \(5\times 5\) m. In this image GNSS real-time position is shown as purple dots, the UWB-based solution is shown as red cross and the reference solution is represented by an orange line (data from the total station). It is possible to observe the absence of reference solution in the indoor corridor part of the path due to the presence of the walls. Therefore, the error analysis was performed only between the common part based on common timestamps. For each total station acquisition, the closest UWB estimation time was identified and compared, while intermediate measurements were discarded as the UWB operates at 4 Hz and the TS at 1 Hz. A check on the linearity of the data and on the time difference was performed in order to verify the presence of time delay between the two system. The two data were both aligned with respect to the GPS time. Figure 9: Pedestrian trajectory obtained by the proposed algorithm expressed in WGS84-UTM zone 32 N coordinates. The results obtained show similar accuracy in the vertical component with respect to the horizontal one, in contrast with the typical behavior of the trilateration estimation, where the vertical accuracy usually is worse due to the weak geometry. The reason is that in this work some of the UWB anchors where placed under the mean horizontal plane as the terrace level is lower than the laboratory level. Moreover, observing the 3D RMSE of the five tests, whose variation correspond to few centimeters, is possible to affirms that, if the environment is always the same, the solution proposed is reliable in time. Comparison between UWB-Only vs. Global Navigation Satellite Systems (GNSS) + UWB  
Considering the overall positioning error of the five tests obtained by the proposed estimation procedure, the empirical cumulative distribution of the errors was computed and compared with that obtained by the real-time solution provided by the UWB only. From this comparison it is possible to observe that the errors estimated by the UWB-only solution are significantly larger than the method proposed. Figure 11 shown this comparison with also the 95 th percentile of the vertical, horizontal and 3D positioning error. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Test 1** & **Test 2** & **Test 3** & **Test 4** & **Test 5** \\ \hline max (m) & 1.56 & 2.72 & 2.09 & 2.12 & 2.20 \\ mean (m) & 0.39 & 0.40 & 0.37 & 0.35 & 0.40 \\ RMSE (m) & 0.46 & 0.46 & 0.44 & 0.41 & 0.48 \\ \hline \hline \end{tabular}
\end{table}