Contactless odometer

An method, comprising:

• positioning a pipeline inspection gauge (PIG) within a pipe;
• positioning a sensor array coupled to the PIG adjacent to an interior surface of the pipe, the sensor array including a plurality of sensing elements configured to output a signal including an amplitude as a function of time, wherein the signal amplitude is dependent upon a distance separating a sensing face of the sensing element from an adjacent surface of a target and a defect present below the adjacent surface of the target;
• moving the PIG within the pipe such that the sensor array is located at a first position with respect to the interior surface of the pipe;
• measuring, by at least a portion of the sensing elements, first signals corresponding to the first position of the sensor array;
• moving the PIG within the pipe such that the sensor array is located at a second position with respect to the interior surface of the pipe, wherein the second position of the sensor array overlaps with at least a portion of the first position of the sensor array;
• measuring, by at least a portion of the sensing elements, second signals corresponding to the second position of the sensor array;
• generating, by a controller, a first defect map based upon the amplitude of the first signals and a relative position of the plurality of sensing elements with respect to one another within the sensor array;
• generating, by the controller, a second defect map based upon the amplitude of the second signals and the relative position of the plurality of sensing elements with respect to one another within the sensor array;
• identifying an overlapping portion of the first and second defect maps;
• and
• determining a translation distance between the first and second positions in at least one direction based upon a location of the overlapping portion with respect to the first and second defect maps.