Evaluating a Static Multibeam Sonar Scanner for 3D Surveys in Confined Underwater Environments

Abstract

Mechanical Sonar Scanning (MSS) is a recent technology that allows sonar to be used for static measurements in the same way as Terrestrial Laser Scanners (TLS), which makes it an attractive tool for underwater infrastructure surveys. Nevertheless, the metrological capabilities of this type of device have been little explored in the literature, particularly in narrow and shallow environments. In this paper, we report on the experimental assessment of a recent MSS, the BlueView BV5000, in a lock. The 3D sonar scans performed with the system suspended from the surface are registered using an innovative algorithm that exploits external measurements from a total station and the symmetry of the structure. We review the different errors that impair sonar data, and compare the resulting point cloud to a TLS model that was acquired the day before, while the lock was completely emptied for maintenance. After correcting a tilt angle calibration error, the maximum difference is less than 10 cm, and the standard deviation is about 3 cm. Visual inspection shows that coarse defects of the masonry, such as stone lacks or cavities, can be detected in the MSS point cloud, while details smaller than 4 cm, e.g., damaged joints, are harder to notice.

Combining photogrammetric and bathymetric data to build a 3D model of a canal tunnel

“…Note that another experiment, dedicated to the assessment of the sensor surveying capacities in a known environment (Moisan et al., 2018) had shown that details smaller than a decimetre could be distinguished, which is consistent with what can be observed here. Defects of significant size in the masonry, such as missing stones or cavities, are easily detected, while finer details, such as damaged joints, are more difficult to distinguish.…”

“…In addition, some defects are probably related to acoustic phenomena, as noticed in Moisan et al. (2018).…”

“…The reader is referred to Moisan et al. (2018) for a quantitative and qualitative evaluation of the MB1350 in a confined environment (in that case, a canal lock), in comparison with the performance of a laser system. Finally, the aperture of the swath is limited to 45°.…”

As-Built 3D Heritage City Modelling to Support Numerical Structural Analysis: Application to the Assessment of an Archaeological Remain

“…It is necessary to highlight the importance of using accurate equipment to capture and model structural and surface deformations on an accurate basis. This can be clearly understood through the work by Moisan et al [19], who evaluate an alternative and recent technique for 3D surveys in confined underwater environments: the Mechanical Sonar Scanning (MSS). Obviously, MSS is aimed at producing point cloud data of, for instance, underwater infrastructure, but its comparison with the accuracy of TLS in the same case study-when no water is present-reveals its crucial role for surface deformations.…”

Multi-Dimensional Underwater Point Cloud Detection Based on Deep Learning

“…The data from the two types of sensors were aligned to construct a full 3D reference model of a canal tunnel. A BV5000 precision test was also conducted in [ 17 ]. The accuracy of the laser data was measured in centimeters so that it could be used as a reference with which to compare the BV5000 data.…”