Abstract: The disclosure provides a method for use in a robotic system for identifying fasteners used in aircraft and other applications. The fasteners include rivets (with no slots), bolts (with two slots) and screws with one or two slots. The method accepts as input a family of related signals which are known to contain symmetry. By computing the mean variance of the zero-meaned cross-correlation signals, the method automatically selects those signals which contain pertinent information while disregarding those signals which do not. The accepted signals are then used to create a composite reference signal which can be used to determine the particular fastener type.