1. A method of tracking translation and rotation of one or more objects within a region of interest, comprising: providing a passive transponder in the region of interest, the transponder having a position and an orientation; generating an electromagnetic field in the region of interest, thereby causing the transponder to transmit electromagnetic signals; mapping said electromagnetic field and said signals as functions of the position and the orientation of the transponder; fixing the transponder to the object being tracked; receiving the signals transmitted by the transponder while the transponder is fixed to the object being tracked; and processing the signals, with reference to said functions, to compute the three-dimensional translational position and three-axis rotational orientation of the object.