Location Identification Using a Magnetic-Field-Based FFT Signature

User indoor positioning has been under constant improvement especially with the availability of new sensors integrated to the modern mobile devices. These sensory devices allow us to exploit not only infrastructures made for every day use, such as Wifi, but also natural infrastructure, as is the case of natural magnetic fields. In this work, we propose a novel approach that takes advantage of the benefits of using the magnetic sensor incorporated in most modern mobile devices, and the negligible variations of the Earth's magnetic field to position an individual with high accuracy. Most importantly, the methodology proposed allows us to avoid the burden of having to collect magnetic information in different directions in order to construct an accurate magnetic map, showing an improvement on methods that require the individuals to construct bigger magnetic maps that contain redundant information such as magnitude in different directions. (C) 2013 The Authors. Published by Elsevier B.V