1 ) A surgical navigation system comprising: a first inertial sensor capable of providing data relating to the position and orientation of said first inertial sensor; said first inertial sensor being attached to a patient's body; a sensor processor capable of receiving said data from said first inertial sensor and calculating the X, Y, Z position and Yaw, Pitch, Roll orientation of said sensor; a mapping processor capable of storing in memory the initial location of a pre-identified point on the patient's body and determining the location of said pre-identified point based on the X, Y, Z position and Yaw, Pitch, Roll orientation of said sensor after the patient's body has moved.