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

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

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ANSI/NIST-ITL 1-2011 - UPDATE 2013 DRAFT VERSIONridge ending or bifurcation (as selected from Table 43 EFS codes for minutia types);otherwise, it shall be marked as unknown type (code 'X'). If the type is unknown, theinformation item radius of position uncertainty/ MRU shall be indicated. As seen in Figure38, the center of the bifurcation should be at the "Y" of the ridge. The theta angle should rundown the valley.Figure 39: Minutia placement for a ridge endingAs seen in Figure 39, the center of the ridge ending should be at the "Y" of the valley. The thetaangle should run up the ridge. Note that the ridge ending location corresponds with that used forthe FBI’s EFTS and INCITS 378, and differs from some vendor-specific approaches. If theprecise location for a ridge ending cannot be ascertained, a radius of uncertainty shall be markedto include the area of possible locations.Figure 40: Minutia placement when type is unknownIn Figure 40, the minutia is placed as for a ridge ending, type / MTY is set to unknown, andthe radius of position uncertainty / MRU is defined to include possible points of intersectionwith neighboring ridges, as shown. The type / MTY of minutia shall be set if theexaminer/encoding process is confident as to type: the “either” type ( Code 'X' from Table 43EFS codes for minutia types) shall be used for all minutiae that are not clearly identifiable as aridge ending or a bifurcation. Because of the frequency with which minutiae appear to be ridgeendings in one impression and bifurcation in another, even in clear images, it is recommendedthat the minutiae type / MTY be used as supporting evidence rather than as a basis forexclusion. All complex minutiae types (crossovers/trifurcations etc) should be marked ascombinations of bifurcation/endings. Unusually distinctive types/combinations of minutiaeshould be marked as unusual minutiae/groups of minutiae in Field 9.324: EFS distinctivefeatures / DIS.The location of the minutia ( the information items 'x' coordinate and 'y' coordinate) , are inMay, 2013 DRAFT VERSION UPDATE 2013 Page 497

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

ANSI/<strong>NIST</strong>-ITL 1-<strong>2011</strong> - UPDATE 2013 DRAFT VERSIONridge ending or bifurcation (as selected from Table 43 EFS codes <strong>for</strong> minutia types);otherwise, it shall be marked as unknown type (code 'X'). If the type is unknown, thein<strong>for</strong>mation item radius of position uncertainty/ MRU shall be indicated. As seen in Figure38, the center of the bifurcation should be at the "Y" of the ridge. The theta angle should rundown the valley.Figure 39: Minutia placement <strong>for</strong> a ridge endingAs seen in Figure 39, the center of the ridge ending should be at the "Y" of the valley. The thetaangle should run up the ridge. Note that the ridge ending location corresponds with that used <strong>for</strong>the FBI’s EFTS and INCITS 378, and differs from some vendor-specific approaches. If theprecise location <strong>for</strong> a ridge ending cannot be ascertained, a radius of uncertainty shall be markedto include the area of possible locations.Figure 40: Minutia placement when type is unknownIn Figure 40, the minutia is placed as <strong>for</strong> a ridge ending, type / MTY is set to unknown, andthe radius of position uncertainty / MRU is defined to include possible points of intersectionwith neighboring ridges, as shown. The type / MTY of minutia shall be set if theexaminer/encoding process is confident as to type: the “either” type ( Code 'X' from Table 43EFS codes <strong>for</strong> minutia types) shall be used <strong>for</strong> all minutiae that are not clearly identifiable as aridge ending or a bifurcation. Because of the frequency with which minutiae appear to be ridgeendings in one impression and bifurcation in another, even in clear images, it is recommendedthat the minutiae type / MTY be used as supporting evidence rather than as a basis <strong>for</strong>exclusion. All complex minutiae types (crossovers/trifurcations etc) should be marked ascombinations of bifurcation/endings. Unusually distinctive types/combinations of minutiaeshould be marked as unusual minutiae/groups of minutiae in Field 9.324: EFS distinctivefeatures / DIS.The location of the minutia ( the in<strong>for</strong>mation items 'x' coordinate and 'y' coordinate) , are inMay, 2013 DRAFT VERSION UPDATE 2013 Page 497

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