1. A system for displaying relative positions of two structures during a procedure on a body, the system comprising: a memory for storing an image data set representing the position of the body based on scans of the body, the image data set having a plurality of data points in known relation to a plurality of reference points for the body; a magnetic field generator for generating a magnetic field; a plurality of magnetic field sensors placed in known relation to at least one of the plurality of reference points for the body, the plurality of magnetic field sensors operable to sense the magnetic field and to generate a position signal in response to the sensed magnetic field; a processor configured to execute instructions to, receive the position signal for ascertaining a location of at least a first sub-plurality of the plurality of magnetic field sensors based upon the position signal, register the ascertained location of at least the first sub-plurality of the plurality of magnetic field sensors and the image data set based on the known relation of at least the first sub-plurality of the plurality of magnetic field sensors relative to the at least one of the plurality of reference points and the received position signal from at least the first sub-plurality of the plurality of magnetic field sensors, generate a displaced image data set representing relative positions of the plurality of reference points for the body during the procedure based on the registered image data set; and learn a geometry of relative locations of at least a second sub-plurality of the plurality of magnetic field sensors placed on the body at a first time to perform an accuracy geometry check at a second time to ensure accuracy after the registration, wherein the second sub-plurality of the plurality of magnetic field sensors placed on the body are configured to remain substantially fixed in the learned geometry between the first time and the second time; and a display to display the displaced image data set generated by the processor to display the relative position of the plurality of reference points for the body during the procedure.