Using Geomagnetic Field for Indoor Positioning

Geomagnetic field variation in support for indoor positioning and navigation has recently attracted considerable interest because of the advantage that technology based on the geomagnetic field has no infrastructure needs. Test using sensitive magnetometers has confirmed that it is possible to use geomagnetic field information for positioning purposes, however there are still issues to be addressed before it can be used in real applications. For example, are the low cost built-in magnetometers in mobile phones good enough for positioning purposes based on “fingerprinting” approaches? Is the geomagnetic field temporally stable for very long period of time? Tests have been carried out using several devices including smart phones. Because geomagnetic field positioning techniques alone may have difficulties, integration with other positioning methods is necessary. Wi-Fi is one of the obvious technology options. One approach is using Wi-Fi to first estimate approximate position, and then apply geomagnetic field information to refine position estimation. An experiment was carried out to test the proposed approach, and the error of fingerprint-based magnetic field positioning was analysed.