Image-based deformation measurement

Image-based deformation measurement (IBDM) techniques entail the use of image sequences for extracting metric information to be compared over time. Their applications may concern several domains, such as civil and mechanical engineering as well as geosciences. The rationale behind IBDM and the methodological classification are discussed in the paper along with some examples of application derived from the experience of the authors. The main advantages of IBDM techniques are the non-contact observational capability, the large coverage on the object along with high acquisition rate, as well as an improvement of the degree of image processing automation. In addition, IBDM is generally a relatively low-cost approach. After a short review of the current state of the art, applications are organized into three main categories: (1) photogrammetric coded-target measurements, (2) surface-point tracking to reconstruct dense displacement fields, and (3) comparison of surfaces obtained from dense image matching. Different camera configurations and geometric models to transform points from the image space to the object space are also discussed.