The position and orientation of remote sensors is determined using pulsed magnetic fields generated from a fixed location. Pulsed magnetic fields are sequentially generated from a plurality of spatially independent components defining a source coordinate frame. The pulsed magnetic fields are...http://www.google.com.au/patents/US5767669?utm_source=gb-gplus-sharePatent US5767669 - Magnetic field position and orientation measurement system with dynamic eddy current rejection 
