Subsequent growth bands are digitized, and files are appended until all growth bands are characterized. This permits three-dimensional digital characterization of structure. This information is used to calculate intermediate micromilling paths. Calculation of Intermediate Sample Paths Because organisms often secrete material in complex patterns, it is difficult to mathematically define smooth curves with which to drill parallel to growth axes. A solution to this problem is to drill linearly between closely spaced points positioned on the curve.
Cubic spline is a robust algorithm for interpolating between sets of points.
This generates sampling paths which are a more precise approximation to actual growth structures than linearly interpolated intermediate points. As the number of points generated by the cubic spline program increases the accuracy of intermediate sampling paths increases. Figure 2 presents a partially digitally characterized otolith. A digital image shows major features of the otolith, and a cartoon of the otolith displays 2 cubic splines that each represent an adjacent annual growth feature. It was determined that 250 intermediate paths could be milled between these particular cubic splines to yield at least 20mg of carbonate for any sample path.