A surgical instrument navigation system is disclosed that allows a surgeon
to invert the three-dimensional perspective of the instrument to match
their perspective of the actual instrument. A data processor is operable
to generate a three-dimensional representation of a surgical instrument
as it would visually appear from either of at least two different
perspectives and to overlay the representation of the surgical instrument
onto an image data of the patient. The image data and the representations
can be displayed on a display.