In the last decades, the rise of life expectancy has accelerated the demand for new technological
solutions to provide a longer life with improved quality. One of the major areas
of the Ambient Assisted Living aims to monitor the elderly location indoors. For this purpose,
indoor positioning systems are valuable tools and can be classified depending on the
need of a supporting infrastructure. Infrastructure-based systems require the investment
on expensive equipment and existing infrastructure-free systems, although rely on the
pervasively available characteristics of the buildings, present some limitations regarding
the extensive process of acquiring and maintaining fingerprints, the maps that store the
environmental characteristics to be used in the localisation phase. These problems hinder
indoor positioning systems to be deployed in most scenarios.
To overcome these limitations, an algorithm for the automatic construction of indoor
floor plans and environmental fingerprints is proposed. With the use of crowdsourcing
techniques, where the extensiveness of a task is reduced with the help of a large undefined
group of users, the algorithm relies on the combination ofmultiple sources of information,
collected in a non-annotated way by common smartphones. The crowdsourced data is
composed by inertial sensors, responsible for estimating the users’ trajectories, Wi-Fi
radio and magnetic field signals. Wi-Fi radio data is used to cluster the trajectories into
smaller groups, each corresponding to specific areas of the building. Distance metrics
applied to magnetic field signals are used to identify geomagnetic similarities between
different users’ trajectories. The building’s floor plan is then automatically created, which
results in fingerprints labelled with physical locations.
Experimental results show that the proposed algorithm achieved comparable floor
plan and fingerprints to those acquired manually, allowing the conclusion that is possible
to automate the setup process of infrastructure-free systems. With these results, this
solution can be applied in any fingerprinting-based indoor positioning system