Enhancing Urban Disaster Resilience for Foreign Tourists in Japan: A Smartphone-Based, SLAM-Enabled Augmented Reality System for Inclusive Flood Risk Communication

Disaster-prone urban areas must support transient and vulnerable populations, including foreign tourists who may face language barriers and difficulty interpreting conventional 2D hazard information. This study developed a smartphone-based augmented reality (AR) system designed to support flood-risk interpretation by foreign tourists in Japan. The system integrates four live external APIs providing location, weather forecast, hazard, and designated emergency evacuation site information, and retrieves these data on demand. Its core function converts hazard map-derived flood-inundation category data into 1:1-scale AR flood visualizations using simultaneous localization and mapping (SLAM) and inertial measurement unit (IMU) data. The system also provides a multilingual interface in English, Japanese, and Thai, weather forecast display, and nearby designated emergency evacuation site identification within a 1500 m radius. This study is positioned as a technical feasibility study. The evaluation comprised a verification of the AR height-placement mechanism against a physical reference at the five display heights used by the system, including the smallest category at 0.3 m (21.5 mm mean absolute alignment error, 1.0–2.3% of the target height); a quantitative SLAM drift evaluation under three movement patterns (at most 1.6 cm mean horizontal and 0.7 cm mean vertical drift after 180 s, within a priori thresholds); and an API response time evaluation under 5G and Wi-Fi (50 measurements per API per network; summed per-API means of approximately 3.99 s and 3.89 s at the endpoint level). The results support technical feasibility under the tested conditions, while effects on comprehension, preparedness, and evacuation decision-making remain for future user studies.