Filtering Methods for Indoor Magnetic Compass

The compass is an essential part of any indoor localization system. Many indoor localization systems use smart phone as a hardware platform and they are all equipped with the appropriate magnetic field sensor. As their outdoor counterpart the indoor compass applications are relies on sensing the Earth magnetic field for determining the direction of the magnetic north pole. However, the indoor magnetic field is very inhomogeneous since the metallic structures used in the building construction significantly distorts the magnetic field inside the building. Therefore, the magnetic compass alone is not precise and reliable in indoor environment. To achieve expectable precision several compensations, fine-tuned filtering methods needs to be applied and other information coming from the positioning, motion detection system needs to combined with the magnetic heading information. This article analyses the most significant magnetic compass errors in indoor environment and proposes filtering and error correcting methods together with their tuning methodology.