CONTRIBUTION TO GEOMETRIC MORPHOMETRICS ...

Ber. Inst. Erdwiss. K.-F.-Univ. Graz ISSN 1608-8166 Band 13 Graz 2008
at most at two points, what is usually the case for ostracods’ outlines (fig. 6). Hence there are
only two pairs of consecutive points in the contour where xi ≥ 0 and xi+1 < 0.
We pass a line through these points, determine the intersection points with the x-axis
and add them to the contour. These intersections will be the starting and end points of the
approximating B-spline curves.
Figure 6: Ostracod contour after standardisation.
The outlining points of the respective region get numbered consecutively clockwise and
are approximated by a B-spline curve of degree p = 2 with a uniform knot vector and
parameter value gathered by a chordal parameterisation. The procedure is explained in
sections 2.1 and 2.2. Figure 7 plots the contour data of an ostracod with its approximating Bspline
curve.
Figure 7: Ostracod contour approximated by a second-degree B-spline curve and its control
polygon.
31