Combining Indoor Positioning Using Wi-Fi Round-trip Time with Dust Measurement in the Field of Occupational Health

[Objectives] The measurement of personal exposure has been attracting increased attention for the control of hazardous substances. Although the combination of location information and personal exposure is considered highly useful, to-this-date, no simple or highly accurate indoor positioning method has been presented. Recently, Wi-Fi round-trip time (RTT) has attracted scientific attention as a highly accurate indoor positioning method. In this study, we investigated the possibility of the use of a combination of this indoor positioning method and small-dust sensors. [Methods] We measured indoor positioning and dust concentration three times during a walk in a simulated factory. A wearable particle monitor was worn on both upper arms, and a smartphone was attached to the helmet for positioning. An ultrasonic humidifier was used to spray sodium chloride solution in the factory. The measurements were conducted three times on different routes on foot (Experiment A, B, C). [Results] In indoor positioning, the error percentages, i.e., measurements that were outside the correct measurement area were 7% (49 s/700 s) in Experiment A, 2.3% (15 s/660 s) in Experiment B, and 7.8% (50 s/645 s) in Experiment C. The dust measurements were also taken without interruption. A heat map was created based on the results of both measurements. [Conclusions] Wi-Fi RTT was able to implement indoor positioning with high accuracy. Thus, the combination of indoor positioning and various sensors can be considered useful for occupational health.