# Loosely Coupled GNSS and UWB with INS Integration for Indoor/Outdoor Pedestrian Navigation +
## 7 Conclusions  
UWB positioning systems are becoming increasingly important for pedestrian navigation in limited environments, both indoors and outdoors, thanks to the numerous advantages they present both in terms of cost and signal transmission. However, the performance of these systems is strongly affected by the environmental conditions in which they operate. GNSS technology is still the preferred positioning system outdoors, thanks to its integrity and accuracy. By combining these two positioning technologies it allows a seamless solution to be obtained, that is capable of obtaining the continuous positioning both outdoors and indoors. This paper proposes a pedestrian seamless navigation methodology, based on a low-cost multi-sensor platform, a data fusion algorithm that integrates GNSS, UWB and INS, and a context awareness approach based on geofencing. In this way the positioning is georeferenced and no longer tied to the local reference system defined by the network of sensors placed around it. The data fusion algorithm is an EKF applied to the specific system which provides an overall horizontal accuracy of 35 cm obtained analyzing 5 different tests. In 3D the solution provides a positioning accuracy on 45 cm. The paper analyzes also very deeply the raw measurements acquired by the UWB commercial system Pozyx in relation with the test-site environment. The ranging error of the system used in this specific cinematic test was around 30 cm which is in line with the performance analysis conducted by the system manufacturer. This level of error is typical of low-cost UWB systems based on the SS-TWR method such as the system presented. However, the DW1000 UWB chipset provides the facilities for message time-stamping and precise control of message transmission times that enable also more advanced algorithms like double-sided two-way ranging (DS_TWR), which has a reduced error even for quite long response delays. This protocol is not implemented at the moment but could represent a solution for further improving the ranging accuracy. Knowing the behavior of  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **UWB-Only** & **GNSS+UWB** \\ \hline max (m) & 12.87 & 2.72 \\ mean (m) & 1.07 & 0.38 \\ RMSE (m) & 1.38 & 0.45 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Overall 3D positioning error.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **UWB-Only** & **GNSS+UWB** \\ \hline max (m) & 9.75 & 2.48 \\ mean (m) & 0.25 & 0.02 \\ RMSE (m) & 1.00 & 0.29 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Overall vertical positioning error.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **UWB-Only** & **GNSS+UWB** \\ \hline max (m) & 6.75 & 1.87 \\ mean (m) & 0.69 & 0.28 \\ RMSE (m) & 0.95 & 0.34 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Overall horizontal positioning error.  
the system in such complex environments (outdoor, indoor, narrow corridor) will provide insights for future research on error rejection.  
Conceptualization: V.D.P. and P.D.; Methodology: V.D.P. and P.D.; Software: V.D.P.; Validation: P.D. and V.D.P.; Formal Analysis: P.D. and V.D.P.; Writing--Original Draft Preparation: V.D.P. and P.D.; Writing--Review and Editing: V.D.P., P.D. and M.P.; Supervision: P.D. and M.P. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Authors would like to thank IEEE for giving permission to reuse some content from the following conference publication. (c)2020 IEEE. Reprinted, with permission, from [[PERSON] [PERSON]; [PERSON]; [PERSON], \"Seamless Navigation using UWB-based Multisensor System.\", 2020 IEEE/ION Position, Location and Navigation Symposium (PLANS), Portland, OR, USA, 20-23 April 2020; pp. 1079-1084.]  
The authors declare no conflict of interest.