Metrological validation of a photogrammetry-based technique

Photogrammetry is a technique that allows one to extract three-dimensional measurements and information about an object from two-dimensional digital images. This techniques finds many applications, and it is particular useful for the documentation of artifacts in the field of cultural heritage. To this purpose, the validation of the dimensional accuracy of the 3D models obtained through photogrammetry is necessary and must be investigated. This paper presents the validation of a photogrammetry-based technique, using a Coordinate Measuring Machine (CMM). The validation employs a reference object manufactured by using a 3D printing machine and designed to be employed in multi-spectral characterizations. The reference is a dodecahedron with the twelve faces coated with several pictorial materials, which are representative of a wide historical period. Thus, the reference can be used also for the integration of multi-spectral imaging data that are not detectable in the visible spectrum. The image acquisition process is fully automated. The quality of such acquisitions is quite good, as it is proved by the presented experimental validation. Some acquisitions both with visible light and with UV light are presented in the paper as well.