1/6/2024 0 Comments Small scallop dredgeThe low resolution images made identification of smaller scallops difficult. Further investigations are necessary to evaluate any underlying bias and to validate how representative these surveys are of the true population. A comparison of the height-distribution from a small-scale dredge survey carried out in the vicinity showed non-overlapping peaks in size distribution, with scallops of a broader size range visible in the AUV survey. After correcting for this difference the estimated heights ranged from cm. An underestimation of approximately cm was seen, which could be attributed to pixel error, where each pixel represented cm. This approach was validated by height estimation of scallops of known sizes. The predicted shell heights were scaled for the distance from the bottom at which the photos were taken. This model successfully predicted a theoretical grid from a frame photographed underwater, representing the inherent lens distortion. A quadratic polynomial model was identified for lens distortion correction. ![]() The average AUV pitch and roll was and deg that resulted in error in ground distance rendering these effects negligible. Prior to height estimation of the identified shells, the distortions introduced by the vehicle orientation and the camera lens were corrected. A small-scale camera based AUV survey of Iceland scallops was conducted at a defined site off West Iceland. An approach is developed to estimate size of Iceland scallop shells from AUV photos.
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