## 3 Results
### Navigation  
The first navigation tests were carried out on a single plane of movement. The main issue was to test the output of the Kalman filter with regard to the navigation, as well as the timings between haptic indications. Figure 11 illustrates the results of one test. The estimated location is illustrated along with the indications given to the user. Some interference was observed due to objects in the area. Figure 11: Single-floor navigation from point A to point B. The red X marks are the route points provided, and the labels represent the navigation modules instructions. An error in the localization estimation near point A results in an erroneous instruction from the navigation module. Figure 10: Localization experiment. Location is tracked along a corridor and up a staircase to the floor above. The red line represents the UWB raw input, and the blue is the value received after the Kalman filter has been applied. The projections of the measurement at three planes are displayed for perspective. The testing phase involved localization and navigation in 3D space, namely movement between floors. The modified final version of the algorithm was used to guide users to the floor above. A sample of the results from the navigation is illustrated in Figure 12. The extension for vertical navigation was simple, since the user could only move between floors using the stairs in known positions. Having only two vibration motors for conveying indications to move between floors proved to be slightly less trivial than the indications for a single floor. Finally, a small number of volunteers were asked to use the haptic navigation feature, and early results were promising. For the most part, after a brief explanation of the different haptic cues, the volunteers were able to follow the short route with little issue. The route was approximately 37 m long and included a floor change. After discarding measurement errors, the results for the 13 test subjects are presented in Table 1.  
After the tests, the participants provided their feedback concerning the performance of these technologies under realistic evacuation scenarios, as well as the perceived ease of use and helpfulness. Positive results were obtained for both the smart lifejacket and the haptic navigation functionality, indicating the overall acceptability of this technology. More specifically, the participants were asked to evaluate the usability of the smart lifejacket following a 1-to-5 rating scale, with 1 corresponding to \"strongly disagree\" and 5 corresponding to \"strongly agree\". The respondents generally agreed that the smart lifejacket was easy to don (mean = 4.54), comfortable to wear (mean = 4.23), that it easily connected with the smart wristband (mean = 4.15) and that it was easy to activate the navigation button (mean = 4.85). In addition to the usability of the smart lifejacket, the respondents' perception on the helpfulness of the haptic navigation was also collected with very positive results. In general, respondents strongly agreed that the haptic navigation on the smart lifejacket was very helpful in the scenario performed during the validation campaign (mean = 9.38). Moreover, they indicated that the haptic navigation would be helpful in a real-life evacuation of a large passenger vessel (mean = 8.77). When asked about the helpfulness of the haptic navigation in case of a real evacuation where they would have been separated from their group and \begin{table}
\begin{tabular}{c c c c c} \hline  & **Minimum** & **Maximum** & **Average** & **Median** \\ \hline Average speed & 0.45 m/s & 0.94 m/s & 0.69 m/s & 0.67 m/s \\ \hline \end{tabular}
\end{table} 
Table 1: Summary results from having test subjects use the lifejacket’s haptic navigation feature. Figure 12: Two-floor navigation following the route from points 1 to 6. Point 3 is located inside the staircase. lost, respondents also ranked the haptic navigation as very helpful (mean = 9.08).