Abstract
In some application fields, such as underwater archaeology or marine biology, there is the need to collect three-dimensional, close-range data from objects that cannot be removed from their site. In particular, 3D imaging techniques are widely employed for close-range acquisitions in underwater environment. In this work we have compared in water two 3D imaging techniques based on active and passive approaches, respectively, and whole-field acquisition. The comparison is performed under poor visibility conditions, produced in the laboratory by suspending different quantities of clay in a water tank. For a fair comparison, a stereo configuration has been adopted for both the techniques, using the same setup, working distance, calibration, and objects. At the moment, the proposed setup is not suitable for real world applications, but it allowed us to conduct a preliminary analysis on the performances of the two techniques and to understand their capability to acquire 3D points in presence of turbidity. The performances have been evaluated in terms of accuracy and density of the acquired 3D points. Our results can be used as a reference for further comparisons in the analysis of other 3D techniques and algorithms.
Highlights
The use of 3D imaging techniques in underwater applications is increasing, in fields such as the survey of submerged artefacts [1], the monitoring of marine flora and fauna [2,3] or the mapping of large areas [4]
We want to understand if the use of structured light under water can improve the acquisition with respect to the passive approach in terms of accuracy and density of the acquired 3D points, in order to provide useful information for the design of a new underwater 3D imaging system and to gather a reference dataset to be compared with the results obtained with other algorithms and techniques
We have proposed a preliminary comparison between two 3D imaging techniques based on active and passive approaches
Summary
The use of 3D imaging techniques in underwater applications is increasing, in fields such as the survey of submerged artefacts [1], the monitoring of marine flora and fauna [2,3] or the mapping of large areas [4]. The main problem in underwater imaging is the poor visibility due to scattering effects [6,7], which influences the image quality and limits the application of imaging techniques in close-range measurements. The use of a whole-field structured-light technique allowed for the reconstruction of 3D scenes regardless of the texture, obtaining acceptable results in the close-range digitization of small objects. We want to understand if the use of structured light under water can improve the acquisition with respect to the passive approach in terms of accuracy and density of the acquired 3D points, in order to provide useful information for the design of a new underwater 3D imaging system and to gather a reference dataset to be compared with the results obtained with other algorithms and techniques. A stereo configuration has been adopted for both the techniques, and we have used the same setup, working distance, calibration and objects
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