The invention relates to an inertial unit for being attached to a rotatable part of a vehicle, the rotatable part being coupled to a power equipment of the vehicle, the inertial unit including: at least one acceleration sensor and/or at least one magnetometer arranged to detect a tilting angle of the rotatable part, and/or at least one counter device arranged to detect rotations of the rotatable part, and at least one gyroscope arranged to detect directions at a rim level of the rotatable part for providing angular information for positioning.