obtaining, using one or more processors of a source device, source device motion data from a source device and headset motion data from a headset worn on a head of a user;

determining, using the one or more processors, correlation measures using the source device motion data and the headset motion data;

updating, using the one or more processors, a motion tracking state based on the determined correlation measures, the updating including transitioning from a single inertial sensor tracking state to a two inertial sensor tracking state, wherein the motion tracking is performed using relative motion data computed from the headset motion data and source device motion data; and

initiating head pose tracking in accordance with the updated motion tracking state.