A new tracking technique is essentially "sourceless" in that it can be
used anywhere with no set-up, yet it enables a much wider range of
virtual environment-style navigation and interaction techniques than does
a simple head-orientation tracker. A sourceless head orientation tracker
is combined with a head-worn tracking device that tracks a hand-mounted
3D beacon relative to the head. The system encourages use of intuitive
interaction techniques which exploit proprioception.