A system (100) includes an elongate instrument (102) having a long axis (104). The elongate instrument includes a first end portion (106 202) along the long axis. The elongate instrument further includes a second end portion (108 208) along the long axis, opposing the first end portion. The elongate instrument further includes an annular location determining device (118) disposed to surround a perimeter of a surface (122 210) of a sub-region (124 212) of the first end portion about the long axis. The annular location determining device generates a signal indicative of a three dimensional location of the annular location determining device, which indicates of a three dimensional location of the first end portion.
