A method and apparatus for determining pose of a transmitter, and by extension the pose of one or more receivers, in an electromagnetic tracking system when the transmitter is allowed to move freely in the physical environment. The method operates in a system that incorporates two separate tracking technologies and an Inertial Measurement Unit, one determining the pose of a device relative to a global reference frame and another determining the pose of the same device relative to a local reference frame, thereby avoiding the latency problem and resulting inaccuracy of pose determinations of known prior approaches.