Advances in Fingerprint Technology.pdf

Orientation for minutiae was defined in relation to the ridge flow by
aligning ridges horizontally. If a minutia produced an extra ridge as one
followed the ridges from left to right, the orientation was termed “positive.”
If a minutia resulted in the loss of a ridge, the orientation was termed
“negative.” The relative position of neighboring minutiae was described
using the two variables: the number of ridges separating the minutiae (the
ridge count) and the distance between the minutiae along the ridge flow
(distance).
For the ridge counts, a convention was introduced to accommodate
minutiae that occurred on the same ridge. This occurs, for example, when
one branch of a fork terminates. Either the upper or lower branch could
terminate, and either would have a ridge count of zero. Stoney and Thornton
assigned either a “+0” or “–0” ridge count in these situations to describe the
upper or lower relationship.
The distance along the ridges was measured in units of ridge intervals
from one minutia, along its ridge, until encountering a transect line running
from the second minutia to the first minutia’s ridge, perpendicularly across
the ridge flow.
Using this system, Stoney and Thornton concisely described neighboring
minutia pairs using six variables: the orientations of the two minutiae, the
types of the two minutiae, the ridge count, and the distance. In all, 2645
minutia pairs were sampled.
Statistical Analysis and Findings
Stoney and Thornton’s statistical analysis of the 2645 minutia pairs revealed
a number of significant findings, which they compared with the work of
other investigators. They qualified their work, however, as strictly applying
only to the epidermal ridges on the distal tips of the male thumb.
General Findings. The method of minutia description was found to be
acceptable to describe fingerprint variation. Ridge densities (number of
ridges per centimeter) were found to be in excellent agreement with earlier
studies by Kingston 20 and Cummins, Wait, and McQuitty. 55
Minutia densities were found to differ from those reported by Kingston, 20
by Osterburg et al., 21 and Dankmeijer et al., 56 with the discrepancy attributed
to differences in the size and location of sampling regions. The findings did
support the generalization made by prior investigators that minutia density
varies significantly among different areas within epidermal ridge patterns. In
the distal region of the thumbprints, however, no difference in minutia
density was seen among the various pattern types.