acknowledgements for ansi/nist-itl 1-2011 - NIST Visual Image ...

ANSI/NIST-ITL 1-2011 - UPDATE 2013 DRAFT VERSIONunits of 10 micrometers (0.01mm). Ridge endings are located at the fork of the midpoint of thevalley (see Figure 39), and bifurcations are at the fork of the midpoint of the ridge (Figure 38).Unknown types are marked as for ridge endings (Code 'E' in information item type / MTY),and with the information item radius of uncertainty / MDU also defined (Figure 40).The direction of the minutia, the information item theta / MTD, is expressed in degrees. Theangle of the minutia is determined by constructing three virtual rays originating at the minutiaand extending 1.93mm (0.064” – about three ridge widths) along each ridge (for a bifurcation)or valley (for a ridge ending). The smallest of the three angles formed by the rays is bisected toindicate the minutiae direction.The information item radius of position uncertainty / MRU is optional. It defines the radiusof a circle centered at the location (X,Y) of the minutia; the circle is sized to include the area ofother possible locations of the minutia, if the precise location cannot be determined (such as dueto poor clarity). If the location is known precisely, the radius of position uncertainty may beomitted or set to 0. The radius of uncertainty is measured in integer units of 10 micrometers(0.01mm), and may overlap the edge of the Region of Interest.The information item direction uncertainty / MDU is optional. It contains an integer from “0”(default) to “180” indicating the precision in the direction (theta) of the minutia, measured indegrees. The resulting direction is Theta±Uncertainty°. Examples of cases in which confidencein direction may be low include cases when the ridge stops or bends close to the minutia so thata good angle measurement cannot be taken, or cases with three equally spaced legs.Note the relationship between Field 9.308: EFS ridge quality/confidence map / RQM andminutiae. In areas of RQM that are green, blue or aqua, the presence and absence of minutiaeis definitive and can be used in future comparison. Otherwise, the regions should be markedyellow.F.6.5Additional featuresF.6.5.1 Field 9.343: EFS ridge edge features / REF instructionsThis field is described in Section 8.9.7.32.Ridge edge features include Protrusions (abrupt increases in ridge width), Indentations (abruptdecreases in ridge width), and Discontinuities (points where a ridge stops briefly):• A protrusion (or spur) is an abrupt increase in ridge width that is not long enough tobe called a bifurcation. An event on a ridge longer than local ridge width shall bemarked as a standard bifurcation with a ridge ending; a shorter event shall bemarked as a protrusion. Protrusions are marked at the center of the protruding area.• An indentation is an abrupt decrease in ridge width. Indentations are marked at the498