3d Reconstruction of an Underwater Archaelogical Site: Comparison Between Low Cost Cameras

Abstract

ABSTRACT:The 3D reconstruction with a metric content of a submerged area, where objects and structures of archaeological interest are found, could play an important role in the research and study activities and even in the digitization of the cultural heritage. The reconstruction of 3D object, of interest for archaeologists, constitutes a starting point in the classification and description of object in digital format and for successive fruition by user after delivering through several media. The starting point is a metric evaluation of the site obtained with photogrammetric surveying and appropriate 3D restitution. The authors have been applying the underwater photogrammetric technique since several years using underwater digital cameras and, in this paper, digital low cost cameras (off-theshelf). Results of tests made on submerged objects with three cameras are presented: © Canon Power Shot G12, © Intova Sport HD e © GoPro HERO 2. The experimentation had the goal to evaluate the precision in self-calibration procedures, essential for multimedia underwater photogrammetry, and to analyze the quality of 3D restitution. Precisions obtained in the calibration and orientation procedures was assessed by using three cameras, and an homogeneous set control points. Data were processed with © Agisoft Photoscan. Successively, 3D models were created and the comparison of the models derived from the use of different cameras was performed. Different potentialities of the used cameras are reported in the discussion section. The 3D restitution of objects and structures was integrated with sea bottom floor morphology in order to achieve a comprehensive description of the site. A possible methodology of survey and representation of submerged objects is therefore illustrated, considering an automatic and a semi-automatic approach.

Camera Calibration Techniques for Accurate Measurement Underwater

“…Photogrammetric surveys for heritage recording, marine biomass or fish population distributions are directly dependent on the accuracy of the 3D measurements. Any inaccuracy will lead to significant errors in the measured dimensions of artefacts (Capra et al 2015), under-or over-estimation of biomass (Boutros et al 2015) or a systematic bias in the population distribution (Harvey et al 2001). Other applications such as structural monitoring or seabed mapping must achieve a specified level of accuracy for the surface shape.…”

Accuracy Assessment of Underwater Photogrammetric Three Dimensional Modelling for Coral Reefs

“…Among a large number of off-the-shelf underwater cameras, the GoPro cameras with their waterproof dive cases are very popular because they are very small, compact, robust, and low-cost, with a high resolution still camera that has high definition video capability. Currently GoPro cameras are increasingly used for underwater photogrammetry, including bathymetry measurement (Schmidt et al, 2012), underwater archaeological surveys (Capra et al, 2015. Advances in software for automated processing and production of 3D models from image sequences greatly expand the usability of low-cost camera systems in photogrammetric applications, including underwater measurement and modelling. Traditional photogrammetric methods require manually controlled processing such as precise measurements of control/tie points for image orientation, camera calibration and geo-referencing processes, which normally leads to considerable effort and expense to process large blocks of images.…”

Quantifying Multiscale Habitat Structural Complexity: A Cost-Effective Framework for Underwater 3D Modelling

“…2016, 8,113 3 of 21 structural complexity to the periods preceding their development, limiting their use to contemporary and future studies [39,42]. As most existing video/photo surveys to date have used monocular cameras, it is clear that there is a great need for a method to produce accurate 3D representations of underwater habitats using data collected by off-the-shelf, monocular cameras [18,19,42]. Such methods would enable the analysis and use of historical data, providing a unique opportunity to understand the role of structural complexity in underwater ecosystems and their temporal trajectory.…”