1. A locating device for use with sterotactic device comprising: electromagnetic position indicating means for generating an output position signal identifying the location of a reference position with respect to a surgical field, and wherein said electromagnetic position indicating means further comprises: an electromagnetic transmitter having an input; an electromagnetic receiver having an output; a magnetic field digitizer having an input connected to said output of said electromagnetic receiver and a first output connected to said input of said electromagnetic transmitter, and a second output for outputting a position signal; a computer having an input connected to said second output of said magnetic field digitizer, a data input, and a display output; and a display having an input connected to said display output of said computer; an imaging scan display system having an input connected to receive said output position signal from said electromagnetic position indicating means and adapted to display a scan image associated with the three dimensional position of said reference position in said surgical field; and a head holder for performing cranial surgery and wherein said head holder supports said electromagnetic transmitter.