1. A non-linear strain gage comprising: a target associated with an object for which at least one of strain and fatigue damage is to be measured and emitting a detectable physical quantity, the target comprising a rectangular binary code symbol including: a solid, continuous outer perimeter; first and second data regions along adjacent sides of the perimeter, each data region comprising at least two rows, each row comprising a plurality of data cells, each data cell representing a single bit of binary data; first and second utility regions along adjacent sides of the perimeter opposite the first and second data regions, each utility region comprising at least two rows, each row comprising a plurality of utility cells of alternating appearance; first and second finder cells at opposite corners of the rectangle; and inner and outer quiet regions distinguishing the first and second data regions, the first and second utility regions, and the first and second finder cells from their background; sensor means for pre-processing the detectable physical quantity emitted by the target and output data representing the physical quantity, the sensor means being compatible with the detectable physical quantity; means for analyzing the data output by the sensor means to define the binary code symbol; and means for measuring the strain on the object directly based on the pre-processed and analyzed data.