TUTORIAL INTRO 4: Underwater photogrammetry systems: optical design, calibration and metrical performances
Underwater photogrammetry has become a key technique for studying and understanding the underwater world in many application fields, such as exploration and mapping, industry and metrology, archeology, biology, etc. Nevertheless, producing accurate three-dimensional measurements underwater is still a challenge if compared to photogrammetric applications on land. The availability of highly customizable and non-standardized underwater photography equipment (e.g. different pressure housings designs, size and materials, dome and flat ports, corrective elements such as the Ivanoff-Rebikoff) poses additional complexity to the process of image formation underwater with subsequent adverse effect to the accuracy of photogrammetric measurements. The tutorial aims at providing the audience with an introduction to the crucial aspects of underwater photogrammetry as 3D surveying technique and independent methods for the assessment of its accuracy potential. The participants will go through the optical fundamentals of underwater imaging, camera calibration approaches, like implicit vs explicit modeling of refraction and their influence on the accuracy of the derived 3D photogrammetric products. During the hands-on session the participants will experience with real as well as simulated underwater datasets (for example through the ISPRS POSER simulator) from archaeology, ecology and subsea metrology applications to critically understand the limits and the benefits of current state-of-the-art photogrammetric processing techniques. Covered topics will include optical design and system setup for single as well as multiple camera configurations, camera network requirements for the determinability of calibration parameters, and accuracy assessment.