Localization in 3-D using beacons of low frequency magnetic field

Traditional localization techniques, such as radar and GPS, rely on RF waves, which require line-of-sight for effective operation. In contrast, applications based on low frequency magnetic fields benefit from high penetration ability to crown canopy, soil, and many other types of media. In previous work we introduced a method for 2-D localization using beacons of low frequency magnetic field. Here, we propose to expand the method for 3-D localization. A mathematical analysis of the beacons' magnetic fields results in closed-form formulas which enable simple localization calculations. The method has been tested using numerous computer simulations showing accurate localization results in noisy environment and in various beacon configurations. A field prototype of the system has been developed and tested in field conditions, validating simulation results. The obtained experimental results show that the mean localization error is smaller than 0.25 m, and the maximal localization error is less than 0.77 m. The simple implementation, together with the fair localization accuracy, make the proposed method attractive for many applications requiring field penetration ability, such as indoor robot navigation, underground cavity mapping, and many more.