Three-dimensional reconstruction of green water on deck based on SLoFTR matching

Accurate measurement of green water on deck is important for assessing wave-induced loads, but conventional gauges provide only pointwise information. This study proposes a stereo-vision method based on SIFT-anchor-guided LoFTR (SLoFTR) for spatially resolved reconstruction of green water on deck. High-confidence SIFT correspondences are used as anchors to estimate epipolar and spatial-support priors, which are introduced into LoFTR matching to improve correspondence estimation in weak-texture regions affected by reflection and foam. The resulting matches are triangulated and transformed into a deck-fixed coordinate system through stereo and zero-plane calibration. Free-running model tests were conducted, and reconstructed elevations were validated at three ultrasonic-gauge locations. Compared with vanilla LoFTR, SLoFTR increased the average numbers of matches and inliers per stereo image pair by 40.9% and 30.5%, respectively, while maintaining a comparable median Sampson distance. Across the three validation points, the Pearson correlation coefficient increased from 0.715 to 0.824 to 0.797-0.946, and the mean squared error decreased by 14.0%-72.3%. SLoFTR also produced more continuous sectional profiles and full-field surfaces. These results demonstrate its potential as a practical non-contact method for spatially resolved measurement of green water on deck.