1. A rectangular binary code symbol for non-linear strain measurement, comprising: 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.