A surgical instrument navigation system comprising: a computer processor a tracking sensor for sensing three-dimensional position information of a surgical instrument and transmitting the position information to the computer processor a memory coupled to the computer processor, the memory including computer instructions that when executed by the computer processor cause the processor to generate an icon representing the surgical instrument positioned in a pre-acquired image of a patients anatomy, the icon of the surgical instrument including a first portion corresponding to an actual position of the surgical instrument and a second portion corresponding to a projection of the surgical instrument along a line given by a current trajectory of the surgical instrument and a display coupled to the processor for displaying the generated icon superimposed on the pre-acquired image.
