Methods of Bidirectional Interpolation and Finite Volume Element for Surface Reconstruction and Volume Calculation of Midwater Trawl

Abstract

Abstract The spatial surface of the midwater trawl was reconstructed with combined interpolation methods of cubic spline, cubic Heimite and polar-coordinate periodic spline interpolation. The results show that the trawl surface obtained only by the ring section method or the vertical section method has a certain deviation, especially when cubic spline is used only in the X direction. When the ring section is combined with the vertical section, and the cubic spline is combined with the cubic Heimite in the X direction, the smoothest feasible trawl surface can be obtained. Two different trawl volume algorithms (volume element method and numerical integration method) were proposed. The finite volume element method can accurately calculate the volume inside the trawl, and the approximation calculation result of the numerical integration method is also very ideal. The numerical integration method is easier to calculate and suitable for the calculation of the trawl volume under any circumstances.