The function allows a non-contact measuring of the length change with an exactly specified reference length and can be used in 2D and 3D projects. The length change can be checked within a project in two or more directions in space. Due to the non-contact optical measuring principle, the measuring results are not influenced by mechanical influences. In addition, GOM Correlate offers the possibility to define a variety of virtual extensometers for the acquisition of longitudinal strains and transverse strains. Another advantage is that virtual extensometers with different initial lengths can be defined and, therefore, local and global strain effects can be examined simultaneously.