A method for tracking a location of a scanner, the method comprising: (a) placing a sensor array of a scanner adjacent to a surface of a target object so that the sensor array overlies a first structural feature of the target object with a reference point on the sensor array at a first position having first X and first Y position coordinates on the surface of the target object which are known, wherein the sensor array is two-dimensional; (b) acquiring a first set of sensor data from a first portion of the target object confronting the sensor array while the reference point is at the first position; (c) converting the first set of sensor data to first scan image data of a first scan image ; (d) translating the scanner over the surface of the target object until the reference point is at a second position at a distance from the first position while the sensor array again overlies the first structural feature; (e) acquiring a second set of sensor data from a second portion of the target object confronting the sensor array while the reference point is at the second position; (f) converting the second set of sensor data to second scan image data of a second scan image; (g) finding feature points in the first and second scan images; (h) determining which feature points found in step (g) are common feature points in the first and second scan images; (i) computing pixel position differences between the common feature points; and (j) calculating a second Y position coordinate of the reference point at the second position on the surface of the target object based at least partly on the first Y position coordinate and the pixel position differences computed in step (i). (a) placing a sensor array of a scanner adjacent to a surface of a target object so that the sensor array overlies a first structural feature of the target object with a reference point on the sensor array at a first position having first X and first Y position coordinates on the surface of the target object which are known, wherein the sensor array is two-dimensional; (b) acquiring a first set of sensor data from a first portion of the target object confronting the sensor array while the reference point is at the first position; (c) converting the first set of sensor data to first scan image data of a first scan image ; (d) translating the scanner over the surface of the target object until the reference point is at a second position at a distance from the first position while the sensor array again overlies the first structural feature; (e) acquiring a second set of sensor data from a second portion of the target object confronting the sensor array while the reference point is at the second position; (f) converting the second set of sensor data to second scan image data of a second scan image; (g) finding feature points in the first and second scan images; (h) determining which feature points found in step (g) are common feature points in the first and second scan images; (i) computing pixel position differences between the common feature points; and (j) calculating a second Y position coordinate of the reference point at the second position on the surface of the target object based at least partly on the first Y position coordinate and the pixel position differences computed in step (i). <EOS>