ANSI/NIST-ITL 1-2011 - NIST Visual Image Processing Group ...

ANSI/NIST-ITL 1-2011Data Format for the Interchange of Biometric and Forensic InformationThis field consists of the following information items:• The first information item (‘x’ coordinate / CXC) is expressed in units of10 micrometers (0.01mm)• The second information item (‘y’ coordinate / CYC) is expressed in unitsof 10 micrometers (0.01mm)• The third information item (Direction / CDI) is optional. This is set to theaverage tangent direction of the two closest ridges as measured 1.63mm(0.064 inches) from the focal point. This is approximately the same as thedirection of the directrix of the best fitting parabola. The direction must beomitted (left empty) for circular whorls, or if the direction is unknown.• The fourth information item (Radius of position uncertainty / RPU)defines the radius of a circle centered at the location (X,Y) of the core; thecircle is sized to include the area of other possible locations of the core, ifthe precise location cannot be determined (such as due to poor clarity). Ifthe location is known precisely, the radius of position uncertainty may beomitted or set to 0. The radius of uncertainty is measured in integer unitsof 10 micrometers (0.01mm), and may overlap the edge of the image.• The fifth information item (Direction uncertainty / DUY) is optional. Itcontains the uncertainty of the direction of the core, in non-negativeinteger degrees. Valid values range from “0” to “180”: a value of “0”(default) indicates a certain direction, while a value of “180” indicates anunknown orientation.Note that if one or more cores are present and the features set is from afingerprint, Pattern Class (PAT) should be defined. Note that this does not meanthat the classification has to be known definitively, but must at least be known tothe extent of excluding plain arches.13.7.25 EFS Field 9.321 Deltas / DELFor fingerprints, one or more deltas are defined for all pattern classificationsother than plain arches, as shown in Table 26. Note that tented arches shouldhave deltas marked if such a structure is present. Accidentals may have anynumber of deltas. Most palmprints contain four interdigital deltas and one carpaldelta. Other delta-like patterns may be defined using this field if such structuresare present in friction ridge images. This field consists of the following informationitems:87DRAFT 2