According to an aspect of the present disclosure, the relative attitude between an inertial measurement unit (IMU), present on a mobile device, and the frame of reference of the vehicle carrying mobile device is estimated. The estimated relative attitude is used to translate the IMU measurement to the vehicle frame of reference to determine the velocity and position of the vehicle. As a result, the vehicle position and velocity are determined accurately in the event of undocking and re-docking of the mobile device from a docking system in the vehicle. The relative attitude is estimated in terms of pitch, roll, and yaw angles.