## 3 Results
### Localization  
The LDER systems use the knowledge of the location of the passengers onboard the vessel's decks to calculate evacuation routes, taking into account the current situation of the ship. Furthermore, knowledge of the position of each passenger is invaluable in locating stray or incapacitated passengers. The field of indoor positioning systems is a scientific area that has been and continues to be heavily researched. Among the many technologies tried, UWB offers the highest accuracy, but most importantly, can cope with multipath better than all of its competitor technologies [36], an important feature given the highly RF-reflective environment created by metal vessels. This is due to the transceivers' high bandwidth (500 MHz or 1 GHz), which leads to time pulses with a duration of less than 2 ns. Any multipath component that has traveled 60 cm more than the direct path can be easily discriminated because it arrives after the end of the pulse of the direct path. We tested the performance of the DW1000 transceivers by taking distance measurements in a hallway, which can be seen in Figure 8, featuring an abundance of metal surfaces that create strong multipath components. In addition, we placed one of the transceivers in front of a door covered with aluminum foil and recorded the corresponding measurements with and without the aluminum foil. The aluminum foil was placed 15 cm away from the transceiver, creating a strong multipath component that has traveled just 30 cm of added distance compared with the direct path. In Figure 9, the error of the distance measurement with and without the aluminum foil is presented. It is observed that the mean error with the aluminum foil is less than 25 cm overall. Consequently, despite the fivefold increase in maximum measurement error from 5 to 25 cm, the absolute accuracy of the system remains sufficient for passenger localization and navigation. Figure 7: The lifejacket after the components have been installed. In order to arrive at a location estimation, distance measurement is not enough. UWB technology is leveraged by installing devices on the smart lifejackets, called tags, that measure their distance from devices installed in fixed, well-known positions called anchors. The area over which we want to track a tag needs to be fitted with anchors, an arduous process with a lot of measuring involved. An important factor in the success of the localization process is the accuracy of the distance measurements and the availability of architectural plans for the area used. Tests were conducted to determine how to spread these anchors over the selected areas. Even with the improved accuracy of the UWB system, a Kalman filter was decided to be implemented, as described previously, in order to improve the quality of the measurements. After doing so, more tests were conducted to calibrate the behavior of the system. One such test is presented in Figure 10. A user wearing the lifejacket walks along a corridor before ascending a flight of stairs to the floor above. Figure 8: **(Left)** Measurement setup to investigate the effect of multipath on the performance of the UWB transceivers. The two transceivers are placed on top of tripods, with one being stationary in front of the door and the second moved along the corridor to take distance measurements at various distances. **(Right)** Close-up of the transceiver in front of the door covered with aluminum foil. Figure 9: Mean error with (red) and without (blue) the aluminum foil covering the door behind the transceiver. What is apparent is that, on a large ship, a passenger equipped with a smart lifejacket can be tracked with reasonable accuracy in real time. This allows for the crew to quickly identify passengers who might be lost or unable to move and quickly dispatch help, something which will shorten the evacuation time. Currently, unaccounted passengers have to be searched for by crew members or located using significantly less accurate localization systems.