Fig. 4. Examples demonstrating the effect of the surface modeling control parameters on the surface, contours and error for the pooled data of this study. The two control parameters are matrix stiffness and number of nodes. In each series of plots the control settings listed at the left are used to generate each of the plots in line to the right. Matrix stiffness refers to the resistance of the smoothing function to allow deviations from the measured data (at the 49 measured points on which the surface is based). The higher this value, the greater influence local points have on the plate form. This can be seen by comparing A and D, where the number of nodes are kept constant and the influence of high stiffness matrix is evident. The number of nodes refers to the elements included in the truncated double Fourier sine series that generates the curvilinear model of the surface. In this case, the greater number of nodes, the more complex the surface shape can be. The influence of this parameter can be seen by comparing surfaces D and G. The analyses performed in the present study used the parameter settings indicated by plots D-F. These maintained much of the complexity of the measured data but linked those points in a more realistic manner than simplistic planar surfaces (Fig. 3A,B). This is indicated by the modest error values (difference between surface model and measured data) for the parameter settings used (error axis resolution in F is an order of magnitude greater than in C or I). For comparison of the optimization predicted for each parameter setting, the optimizations are provided (as in Fig. 3F). General predictions are consistent even over the wide range of control parameters illustrated, but the excessive smoothing of the extreme options removes all subtle features of the surface and increases overall error.