Let us analyze the curves in Figure a from this point of view. There are four curves in the figure, which from the left to the right (upper parts of the curves) represent singular values of matrices computed for even sampling in sloth, slowness, velocity and alacrity domains. This is the succession according to the above criterion. The velocity and alacrity curves have evidently worse behavior. The difference between the sloth and slowness curves is much less. The difference between the sloth and slowness curves in Figure d is almost nil. In this figure high velocities were not included. In the region of high velocities slowness has worse behavior than sloth.
Singular values for matrices are in Figure b. They should be the square roots of those in Figure a. This relationship holds for about the first 150 singular values. It does not hold for the rest of the values because of the limited computational precision (double precision used).