Head tracking with adaptive reference

A system of providing an adaptive reference orientation usable for determining a relative head orientation of a user, the system comprising:

• a head sensor configured to sense head data, the head data defining a head orientation associated with a user;
• one or more second sensors physically and functionally separate from the head sensor, the one or more second sensors being configured to sense second data, the second data being indicative of changes of a current frame of reference of the user;
• and
• a processing unit operably coupled to the head sensor and the one or more second sensors, the processing unit being configured to repeatedly provide:
• a) receiving head data sensed by the head sensor, the head data defining a head orientation;
• b) receiving second data sensed by the one or more second sensors;
• c) using currently received second data to obtain a new adaptive reference orientation by moving the current adaptive reference orientation at least partly towards the defined head orientation by an amount which is varied at least partly in accordance with the currently received second data;
• d) computing the head orientation relative to the new adaptive reference orientation;
• and
• e) using the new adaptive reference orientation as a current adaptive reference orientation for a next repeat of operations a)-d).

A non-transitory computer-readable memory tangibly embodying a program of instructions executable by a computer for executing a method of providing an adaptive reference orientation usable for determining a relative head orientation of a user, the method comprising:

• repeatedly providing:
• a) receiving head data sensed by a head sensor, said head data defining a head orientation associated with a user;
• b) receiving second data from a second sensor physically and functionally separate from the head sensor, said second data indicative of changes of a current frame of reference of the user;
• c) using currently received second data to obtain an new adaptive reference orientation by moving the current reference orientation at least partly towards the defined head orientation by an amount which is varied at least partly in accordance with the currently received second data;
• d) computing head orientation relative to the new adaptive reference orientation;
• and
• e) using the new adaptive reference orientation as a current adaptive orientation for a next repeat of operations a)-d).