Magnetic direction finding device with improved accuracy

Claim 1

Apparatus for accurately measuring the relative positioning in three-dimensional space of a first object relative to a second object when said objects are in proximity to surrounding structures tending to distort magnetic field patterns, comprising: (a) a first plurality of mutually orthogonal flux transmitting coils affixed to said first object to define a coordinate frame of reference; (b) a second plurality of mutually orthogonal flux receiving means affixed to said second object; (c) means for energizing each of said transmitting coils with a voltage having a number of harmonically related frequency components sufficient to characterize the distortion of said magnetic field patterns; (d) means coupled to said plurality of receiving means for periodically sampling the instantaneous analog voltage induced in said receiving means by the transmitted flux and converting said analog voltage samples into a corresponding digital value; (e) FFT processor means coupled to receive said digital values for determining pitch and yaw angles of said first object concurrently at said number of harmonically related frequencies; and (f) computing means coupled to receive digital values defining the multiple pitch and yaw angles to the multiple harmonically related frequencies for mathematically extrapolating said multiple pitch and yaw angles to produce an estimate of a pitch and yaw angle associated with an arbitrarily low frequency at which distortion of said magnetic field is substantially zero.