The present invention relates to a method for estimating the value of the angle of the direction of motion or of the walk of a person who carries a device capable of measuring the basic quantities related to his/her own inertia such as a common smartphone. The device is capable of measuring for example acceleration and angular rotation and to determine its orientation relative to Magnetic North. The estimation method in question is particularly suitable for estimating the direction angle of the individual's motion regardless of how the individual carries the device able to measure the main inertial quantities and consequently this method solves the problem of the determination of the relative attitude between the reference system of the carried device and the user reference system that moves within a generic absolute reference system.