# ISO IEC 19794-2:2011 pdf – Information technology一Biometric data interchange formats一 Part 2: Finger minutiae data

ISO IEC 19794-2:2011 pdf – Information technology一Biometric data interchange formats一 Part 2: Finger minutiae data.

The maxarium number of minutiae accepted Is therefore an implementation dependent value and shall be indicated in the Biometric Information Template, if the default value is not used (see Annex D).

A card may also require a special ordering of the minutiae presented in the biometric verification data. The ordering sdieme shall be indicated in the Biometric Information Template (see ISOIIEC 19785 and ISO1IEC 7816.11), if the default value is not used,

9.3.2 Removing minutiae for card processing

If the number of minutiae exceeds the maximum number the card indicates it can accept, then minutiae shall be removed according to one of the following two options:

• Minutiae with the largest Euclidean distance from the centre of mass shall be removed first, The centre of mass shall be computed before any minutiae are removed.

• II minutia quality data is available, minutiae of the lowest quality are removed first When any two

minutiae share the same quality value, the one with the largest Euchdean distance from the centre of mass of

a minutia set shall be removed first. The centre of mass shall be computed before any minutiae are removed.

For minutiae that have the same quality and Euclidean distances, remove ridge ending first, and for minutiae

of the same type, remove minutia with largest angle first.

Removal shall be conducted before any needed sorting of the minutiae.

This procedure shall apply to both the enrolment of a reference template, and the preparation of a verification

template.

9.3.3 Lack of minutiae

If the number of minutiae is fewer than the minimum number indicated by the card the following options should be considered:

• re-acquisition of a sample from the subject

• use of a different finger

• prompt user or operator.

The implementation shall not assign fictional minutiae.

9.3,4 Biometric comparison algorithm parameters

Biometric conipanson algorithm parameters are used to Indicate Implementation specific values to be observed by the outside world when computing and structuring the biometric verification data. They can be encoded as DOs embedded in a coinpanson algorithm parameter template as defined in l$O1IEC 19785-3:2007, Clause 11. Table 15 lists the DO biometric comparison algorithm parameters.

9.4.4 CartesIan X.Y

Cartesian x-y stands for an ordering scheme, where first the x-coordinate is compared and used for ordering. When ordering by ascending Cartesian x-y coordinates, the minutia with minimum x-coordinate becomes the first minutia lii the ordered sequence. The minutia with the second smallest x-coordenate becomes the second minutia in the ordered sequence. Thés process continues until the minutia with maximum x-value becomes the last minutia In the ordered sequence. If the x-coordlnates in two or more mwiutiae are equal, the y-coord.nate is compared for ordering.

9.4.5 CartesIan Y.X

Cartesian y-x stand for an ordering scheme, where first the y-coordinate is compared and used for ordering. If

the y-coordinates in two or more minutiae are equal, the x-coordinate is compared for ordering.

9.4.6 Angle

Sorting a minutiae list by angle Is done as follows. As defined in a previous section the angle of a minutia begins with value 0 to the right horizontal axis and increases counter-clockwise When ordenng by increasing angle, the minutia with the minimum angle value in the ordered sequence becomes the first minutia in the ordered sequence. The minutia with the second smallest angle value becomes the second minutia in the ordered sequence. This process continues until the last minutia in the ordered sequence is defined as the minutia with maximum angle value. No rules for subordering are defined, if the angle values in two or more minutiae are equal Any possible ordering sequence of the minutiae with the same angle value is allowed in this case.

9.4.7 Polar

Polar is an ordering sequence by ascending or descending polar coordinates, First of all, a virtual coordinate root is defined as the center of mass of all mmubae The polar coordinates of every minutia are computed as the relative distance and angle to this root coordliate. Without loss of generality, the process of ascending ordering with polar coordinates Is described. The minutia with minimum EucIiean distance to the root becomes the first minutia in the ordered sequence. The minutia with the second smallest distance to the root becomes the second minutia in the ordered sequence. This process continues until the mmutia with maxinum distance to the root becomes the last minutia in the ordered sequence. If the root-distance of two minutiae or more is equal, the angle of these minutiae is compared The minutia with the smallest angle as defined in 651 becomes the next minutia In the ordered sequence.