Evaluation of reachability and promptness in delivering disaster and evacuation information using an augmentation signal of the Quasi-Zenith Satellite System

There can be many failures in the ground communication infrastructure following an earthquake such as the Great East Japan Earthquake. In such an event, disaster management agencies may not be able to alert residents to a Tsunami Warning or provide evacuation information. Consequently we have developed the RedRescue system, which broadcasts disaster notifications and evacuation information using the Ll-SAIF signal - an augmentation signal of the Quasi-Zenith Satellite System (QZSS). A feature of RedRescue is that, in the case of a breakdown in ground communication, disaster and evacuation information can be received using a GNSS receiver (e.g., a smartphone) without using a special device such as a satellite phone. This paper reports on the results of simulating the effectiveness of the system in transmitting disaster and evacuation information in terms of reachability and promptness. Specifically, we compared the performances of RedRescue and existing systems such as the Emergency Broadcast systems. For reachability of information, the RedRescue has a greater reach than the Emergency Broadcasts for the same reception ratio dealing with the arrival time of a tsunami. We defined the promptness of information as time taken to reach a determined percentage of the evacuees who received the information For promptness of information, RedRescue reaches the determined percentage faster than the Emergency Broadcasts. Hence, when notifying users of a disaster, we found that RedRescue was more effective than existing systems in terms of reachability and promptness because it was able to transmit information to many users faster than existing systems without being affected by the position of the user.