Forward-Backward Approach for 3D Event Localization Using Commodity Smartphones for Ubiquitous Context-Aware Applications in Civil and Infrastructure Engineering.

An inexpensive and robust 3D localization system for tracking the position of a user in GPS- or WLAN-denied environments offers significant potential for improving decision-making tasks for civil and infrastructure engineering applications. To this end, an infrastructure-free approach for 3D event localization on commodity smartphones is presented. In the proposed method, the position of the user is continuously tracked based on the smartphone sensory data (the Forward approach) until the user reaches a certain event. Here, an event location refers to the 3D location of a user conducting value-added activities such as tasks involved in emergency response and field reporting of operational issues. Once an event is observed, the motion trajectory of the user is backtracked from the postevent landmark to reestimate the location of the event (the Backward approach). By integrating probability distributions of the Forward and Backward approaches together, the proposed method derives the most-likely location of the event. To validate the proposed approach, seven case studies are conducted in a multistory parking garage. The experimental results show that the probabilistic integration of the localization results from the Forward and Backward dead reckonings can produce more accurate 3D localization results when compared to a single best estimate from a one-way dead reckoning process. Lessons learned from several real-world case studies and open research challenges in improving localization accuracy are discussed in detail. [ABSTRACT FROM AUTHOR]