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 outer perimeter, each data region comprising a number of data cells, each data cell representing a single bit of binary data, the first and second data regions having inner sides inwardly offset from the outer perimeter; first and second utility regions along adjacent sides of the outer perimeter opposite the first and second data regions, each utility region comprising a number of utility cells of alternating appearance, the first and second utility regions having inner sides inwardly offset from the outer perimeter; an inner perimeter defined by the inner sides of the first and second data regions and the first and second utility regions; 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, the outer quiet region being outward of the outer perimeter and the inner quiet region being inward of the inner perimeter.