An algorithm which can obtain the global walking direction

Abstract

This paper proposes an algorithm to obtain the global walking direction despite magnetic field interferences indoor. This algorithm can be applied to the phone's compass. If the user is walking in the opposite direction of the phone's compass (North). The user's global walking direction would be “South”. The phone's compass equipped a magnetometer collects data. This algorithm treats these data as signals and eliminates some high frequency components by passing them through a low pass filter. This algorithm opportunistically selects three consecutive vectors which are not parallel. Then it decomposes the three vectors into two directions. One is the earth's magnetic field vector. The other is the interference vector. It subtracts the earth's magnetic field vector from the compass reading vector and offers the interference vector. Then this algorithm calculates the coordinates of the pairwise intersections of the three interference vectors. Experiments show that the right geomagnetic north vector makes the locus of intersection points forms likes an oval or a closed loop. The accuracy of this algorithm is higher than the traditional compass. The global walking direction can be outputted by comparing the walking direction against this geomagnetic north vector.