The lack of reliable GPS signals inside buildings has been an obstacle to determine accurate indoor positioning. Using advanced dead reckoning algorithms based on fused data provided by an Inertial Measurement Unit (IMU), Portuguese researchers from Fraunhofer AICOS (Porto, Portugal) have overcome this issue. The Precise Indoor Location (PIL) is an accurate indoor location technology with sub-meter level accuracy that allows indoor navigation using a smartphone. PIL has been designed to support several real usage scenarios, such as when the smartphone is in a pocket or while in calling or texting.
Indoor location systems are an important enabling technology for applications such as indoor navigation, public safety, security management and ambient intelligence, representing huge potential regarding advertisement and retail businesses. Pedestrian navigation systems (PNS) have recently emerged as a solution for the indoor positioning problem regarding the lack of accuracy. These systems rely on dead reckoning algorithms which are solutions based on the fused data provided by the Inertial Measurement Unit (IMU) on the smartphone that can then be used to evaluate one’s current position by using a previously known one.
The patent pending indoor tracking solution developed at Fraunhofer AICOS differs from the classical dead reckoning approaches by employing filtering techniques that are based on the knowledge of human gait. Our body produces cyclic movement patterns as a consequence of the alternate movement of the legs while walking. The knowledge of human walking behavior enabled the research team to link the data acquired by the IMU on the smartphone to the gait cycle, making possible to detect each time a step is taken and to quantify the amount of movement produced by the person. Additionally, the direction of movement is evaluated and corrected taking into account these human motion models.
Since all dead reckoning solutions are subject to cumulative errors, navigational aids are needed in order to give accurate information, not only to correct positional errors but also to calibrate dead reckoning algorithms. The aided information can be gathered from any system that can provide absolute reference points with increased resolution. Regarding this matter, the approach of the Fraunhofer AICOS’ researchers relies on the Ultra-Low Frequency Magnetic Communication (ULF-MC), a patent pending communication technology developed at Fraunhofer AICOS in 2012 that when combined with a last fix from a Global Navigation Satellite System (GNSS) is able to provide absolute coordinates inside a building. ULF-MC has been awarded the Galileo Master prize at the European Satellite Navigation Competition in 2012.
ULF-MC is as easy and useful as satellite-based navigation and allows receiving relevant location-based information and developing indoor navigation solutions. It consists of a wireless technology for smartphones based on the generation of ultra-low frequency varying magnetic fields. By extending outdoor navigation systems with simple, low-cost infrastructure for indoor areas, ULF-MC provides exact coordinates or related location IDs that can be transferred to absolute positions involving the last GNSS fix. This system can be used for multiple applications such as aided indoor navigation solutions, location-based services and mobile payment.
The initial developments of the PIL technology led to a prototype that is already under performance tests. In this first version, the system is prepared to work in the most common uses of a smartphone, including, walking with the smartphone in the pocket, making a phone call or sending a text message. On the one hand these tests revealed highly promising results. On the other hand, the results allowed researchers to identify additional options for improvements which have been validated already experimentally and were leading to the desired sub-one-meter accuracy of the system.
The researchers from Fraunhofer AICOS are now focusing their work on integrating the different dead reckoning algorithms to provide a robust solution for the emerging indoor location market that outperforms the existing, often infrastructure-heavy and thus costly solutions. They are also implementing and testing additional reference systems beyond ULF-MC. A commercial version and a related spin-off are already in preparation.