Assisting elderly and/or visually impaired people in locating and navigating in an indoor environment is a very commendable aim. It motivated Tsirmpas et al. to tackle the issue. The main challenge of indoor navigation is that GPS, which works outdoors, cannot be used. But today’s technologies open new possibilities to solve indoor navigation. There are several approaches: radio-frequency identification (RFID), Bluetooth, ultra-wideband (UWB), Wi-Fi, microelectromechanical systems (MEMS), near field communication (NFC), infrared light emitting diode (LED), ultrasound, vision-based systems, and so on. A particular challenge of indoor localization is accuracy and dynamic adaptivity to different surroundings.

The authors chose to base their solution on RFID and ultrasound pilots (within a wearable module), which allowed them to calculate also with obstacles in a path. To make it work for any navigation space, the authors present its discretization into points. A path is represented as a set of vectors. To calculate the shortest path, Dijkstra’s algorithm is employed. To deal with obstacles (either expected or not), they define a calculation based on probability. Three basic scenarios are identified that can occur during navigation, and calculation properties for them are derived. The authors deal also with RFID’s antenna properties, especially capacitance, to choose the most suitable one.

Having elaborated a thorough conceptualization of their approach, the authors describe an example of the devised system architecture and a simple experiment design. Four blindfolded volunteers were used for evaluation. While any observations acquired during their interaction with the devised system are potentially interesting, their number is too low to allow for any relevant conclusions. The result reported in the paper is a system that apparently works, but it should be evaluated with a larger group of testers that is more oriented toward future users, within wider indoor spaces.

The paper reports on an interesting piece of innovative research. It is well motivated and presented. Researchers in the field of indoor navigation might find it inspiring.