The basis for the Data Interpretation section of the GFP 1000 tutorial is described using Mohr's Circle. Mohr's Circle is a graphical representation of the relationship between principal strains and shear strains. The Grey-Field Polariscope produces 4 specific pieces of data, shear 45, shear 0, shear max, and shear direction. Each of the four data sets are represented in the diagrams on the following pages. Use the buttons to the left to go directly to one of the four data sets or used the arrows above to page through from one to another.