A system (10) to navigate an instrument (52) relative to a portion of a patient's (14) anatomy, comprising an instrument (52) having a shaft (90) that extends from an engagement portion (84) to a working end (87), wherein said engagement portion (84) has a first long axis and said working end (87) has a second long axis, wherein the first long axis is non-linear with said second long axis； a member (80) selectively engageable to an engagement end (86) of said engaging portion (84) such that said member is operable to be engaged and disengaged from said engagement end； a first tracking sensor (58) interconnected with said instrument at said working end； and a tracking system operable to track said first tracking sensor (58), said tracking system further comprising a probe (66) having a second tracking sensor (58)； wherein said first tracking sensor (58) and said second tracking sensor (58) can be tracked by said tracking system； wherein said tracking system is operable to determine an orientation of said member relative to said first tracking sensor when said member is engaged to said engaging end； said tracking system configured to determine a plane (Y) of said first member by determining at least three points (Y1, Y2, Y3) on said member by touching said probe (66) to each of said at least three points, and said tracking system configured to determine a vector (X) extending normal to and through the determined plane (Y) defined by said member from a center of the member by tracking the probe when touched to a point (X1) at an apex at a top of the member, wherein the vector (X) defines at least a portion of a geometry of said member (80), wherein said tracking system is operable to determine an angle between said vector (X) and said patient, and wherein said vector (X) extends through a point at said apex of said member.
