Application of Spatial Interpolation and Central Radiation Method in the Surface Reconstruction and Volume Calculation of Midwater Trawl

This paper uses spatial interpolation to reconstruct the three-dimensional surface of midwater trawl, and the trawl surface is successfully reconstructed with a variety of different surface patch functions and weight functions. The entire internal space of the trawl is decomposed into a finite number of tetrahedral volume elements that are seamlessly connected in sequence. Two different methods (central radiation method and signed volume method) are proposed to calculate the trawl volume. Compared with the Delaunay triangulation, the layered free triangulation method proposed in the present study can obtain a smoother and more reasonable trawl surface. By combining the weight functions (5), (6), (7), and (9) with the two-order surface patch function (10), taking four coordinate points to fit the surface patch function for the cod-end of the trawl, and taking eight coordinate points to fit the surface patch function for the other parts, the better and smoother trawl surface can be obtained. However, the interpolation surface, obtained by combining the weight function (7) and the surface patch function (10), should be the best result, because the interpolation surface is naturally smooth, and the gradient is gentle and reasonable. The symbolic volume method has wider applicability.