Comparison between the two methods. The noticeable ring-shaped ripples at the bottom of Method 1 are caused by the interpolation of spherical coordinate data into Cartesian coordinates, as shown in panels (a)–(c). The barely noticeable ring-shaped ripples at the bottom of Method 2, shown in panels (d)–(f), result from the conversion of the original data and are unrelated to the implementation of the method itself.