Multimedia photogrammetry 2.0. A first step for underwater cultural heritage application

The research is framed in multimedia photogrammetry, a specific domain aimed at acquiring geometric information about static objects immersed or semi-submerged in a liquid through one or more cameras external to the liquid. If the liquid is water, this field belongs to the broader field of applied metrology for analysing and understanding the aquatic world. Specifically, the various passive sensing techniques for acquiring Underwater Cultural Heritage (UCH) in shallow water are central to understanding the research domain's underlying issues. Our research is framed in the domain, implementing the automatic analysis to estimate a priori (and correcting a posteriori) the camera's behaviour under certain conditions for acquiring submerged or semi-submerged objects. The first analytical results are framed in a two-year project, which aims to define a behaviour model in a controlled environment with encoded targets and stereo-photogrammetry, automatically extracting the camera orientation parameters under different water height conditions. A planar reproduction of a CH artefact, which simulates an immersed architectonic floor, has been applied to validate the process in a first case study, testing the system's capacity to extract the correct coordinates of the image. At the end of this first experimental phase, the aim is to define a model for the behaviour of water deformation. It will make it possible to predict and correct the water refraction by calculating the correct coordinates within the liquid. In the future, this model will be tested under different and incrementally more complex acquisition conditions. The global project's primary goal is to arrive at the application of this model in an uncontrolled environment for the survey of UCH in shallow water.