The strain measurement system of XTSM sheet metal forming grid takes  

stamping image with high resolution digital SLR camera or measuring head

with industrial CCD camera, and then calculates the spatial coordinates of

small circle points produced in multiple photos with high accuracy by

photogrammetry. The deformation and strain distribution of parts, hot spot

area and thickness variation of sheet metal can be obtained (assuming the

volume remains unchanged), and calculate 3D Deformation of sheet metal.