1 

A Study on Accuracy and Problems in using ISO/IEC 19794-2 Finger 

Minutiae Formats for Automated Fingerprint Verification 

Takahiro Yoshida, Seiichiro Hangai 

Department of Electrical Engineering, Tokyo University of Science 

1-14-6 Kudan-kita, Chiyoda-ku, Tokyo, 102-0073, Japan 

Abstract. For the purpose of clarifying the problems in 

using ISO/IEC 19794-2 formats, the minutiae detection 

software MINDTCT and the fingerprint matching 

software BOZORTH3 included in NBIS were modified 

to accept the standardized fingerprint data. From 

experimental results, the EERs of authentication system 

using the ISO/IEC 19794-2 formats become slightly 

worse than that of the system using original XYT 

format. The degradation of EERs, 0.1%~0.77%, shows 

the validity of the use of the ISO/IEC 19794-2 formats 

from the viewpoint of the EER. However, many 

problems such as no existence of the minutiae quality 

and header field in Card formats, or limitations of the 

number of minutiae and maximum size of fingerprint 

image are found in conversion and authentication 

processes. In this paper, accuracy and problems in 

accepting the ISO/IEC 19794-2 data format are given. 

Keywords: Fingerprint authentication, Minutiae, 

ISO/IEC19794-2, EER 

Introduction 

In considering usability and interoperability of 

automated fingerprint recognition and authentication 

system, the ISO/IEC 19794 Part 2 [1] specifies the 

biometric data interchange formats for finger minutiae 

data. This standard defines “Finger Minutiae Record 

format”, “Normal size Finger Minutiae Card format”, 

and “Compact size Finger Minutiae Card format”. 

However, these formats have different resolution in 

minutiae coordinates and direction angle. In addition, 

the information involved in the card format is limited. 

Furthermore, in the format, the fields of additional 

information such as fingerprint image size and minutiae 

quality value is not included. It is easily expected that 

these differences influence to automated fingerprint 

authentication accuracy in conversion process. 

Therefore, it is necessary to investigate the problems 

and influence in accepting the ISO/IEC 19794-2 data 

formats. 

In this study, the most popular minutiae detection 

software, e.g., MINDTCT, and the minutiae based 

matching software, e.g., BOZORTH3 included in NBIS 

(NIST Biometric Image Software) [2], are modified to 

accept and feed through ISO/IEC 19794-2 data formats, 

and used for automated fingerprint authentication. The 

problems and influence on the authentication accuracy 

in accepting the ISO/IEC 19794-2 data formats are 

examined in this work. 

2 Definition of Minutiae Data in the 

ISO/IEC 19794-2 

2.1 X and Y Coordinates of Minutia Location 

The definition of X and Y coordinates of minutia 

location of each format is shown in Table 1. The XYT 

format is a minutiae text file which is used for 

transmitting the minutiae data from the MINDTCT to 

the BOZORTH3. For the Record format, 14 bits are 

assigned for the XY coordinates respectively. The 

resolution is 0.01 mm/unit in the Normal size format 

and 0.1 mm/unit in the Compact size format. 

There is no error in the coordinate’s conversion from 

the XYT to the Record format, because the resolution of 

coordinates is same. However, the Card formats involve 

errors in the coordinate’s conversion from the pixel unit 

to the metric unit. 

The origin of the coordinate system of the ISO/IEC 

19794-2 formats is the upper left corner of the original 

image with X increasing to the right and Y increasing 

downward. In contrast, the origin of the XYT format is 

the lower left corner. Only the value of vertical size of 

the fingerprint image is necessary to convert the origin. 

Table 1. Definition of coordinates of minutia location. 

Format Resolution Coordinate 

XYT format 

(Used in NBIS) 

Depend on 

fingerprint 

image 

1 pixel, 

Integer 

value 

y 

0 x 

ISO/IEC 19794-2 

Record format 

Depend on 

fingerprint 

image 

1 pixel, 

14bit 

binary 

0

y 

x 

ISO/IEC 19794-2 

Card format 

(Normal size) 

Fixed 

2540ppi 

0.01mm, 

14bit 

binary 

0

y 

x 

ISO/IEC 19794-2 

Card format 

(Compact size) 

Fixed 

254ppi 

0.1mm, 

8 bit 

binary 

0

y 

x 
 

 

 

 

 

 

 

 

 

 

Table 2. Definition of X and Y coordinates. 

Format Resolution Field Type 

XYT format 

(Used in NBIS) 1° Text 

ISO/IEC 19794-2 

Record format 1.40625° 8bit 

ISO/IEC 19794-2 

Card format 

(Normal size) 

1.40625° 8bit 

ISO/IEC 19794-2 

Card format 

(Compact size) 

5.624° 6bit 

2.2 Angle of Minutia Direction 

The definition of the angle θ of minutia direction of 

each format is shown in Table 2. The resolution of the 

angle is different in each format. For example, in the 

XYT format, the resolution is 1°. However, the 

resolution in the Record format and Card format 

(Normal size) is 1.40625°, and 5.624° in the Card 

format (Compact size). Therefore, the ISO/IEC19794-2 

formats have errors in the angle conversion. The 

definitions of directions of ridge ending, and bifurcation 

valley are also different between the XYT format and 

the ISO/IEC 19794-2 formats. 

3 Experiment of Automated Fingerprint 

Verification 

3.1 Experimental Condition 

The NIST Special Database 9, Volume 1 [3] is used as 

the test dataset for automated fingerprint verification 

experiments. This database consists of mated 

fingerprint image pairs for each person and each finger. 

The fingerprint images named “File” are used for 

making reference, and ”Search” are used for 

verification process in the experiment. The finger print 

images are 832 pixels width by 768 pixels height, and 

gray scale that have 8 bit depth with the resolution of 

500 pixels/inch. 

In this experiment, two kinds of dataset are used. The 

test dataset 1 consists of 1800 fingerprints. The mate 

900 fingerprints are used as the reference data, i.e. 90 

persons X 10 fingers. The other mate 900 fingerprints 

are used for the verification data. The fingerprint 

verification experiments are done with round robin. The 

False Reject Rate (FRR) is calculated after 900 

verification tests, and the False Accept Rate (FAR) is 

also calculated after 809100 verification tests. The test 

dataset 2 consists of 200 fingerprints. The mate 100 

fingerprints are used as the reference data, i.e. 10 

persons X 10 fingers. The other mate 100 fingerprints 

are used for the verification data. The FRR is calculated 

after 900 verification tests, and the FAR is also 

calculated after 9900 verification tests. 

3.2 The Sequence of the Experiment 

The sequence of the experiment is as follows; 

(1) The fingerprint images of Special Database 9 are 

converted to RAW formatted images by the conversion 

program DJPEGLSD, which is a part of the NBIS. 

(2) The RAW formatted fingerprint images are 

converted to WSQ formatted images by the image 

compression program CWSQ, which is also a part of 

the NBIS. The bit rate setting of the CWSQ is 2.25. 

(3) The MINDTCT software loads the WSQ formatted 

fingerprint image and feed through the extracted 

minutiae to each formatted files. The number of output 

minutiae is limited to 150 with the order of quality. The 

XY coordinates of minutiae of the Card format 

(Compact size) are normalized by the size of fingerprint 

image. 

(4) The BOZORTH3 software loads the minutiae files 

and calculates matching score. 

(5) The characteristic curves of the FAR and FRR 

against the threshold value are calculated from the 

matching scores. Equal Error Rate (EER) is decided 

from the threshold when the FRR is equal to the FAR. 

3.3 Experimental Results of the Verification 

Accuracy 

In this experiment, the verification accuracy of each 

format is examined with the test dataset 1. This 

experiment is done by the best experimental conditions 

to avoid the problems described in section 4. The 

comparison of EERs of each format is shown in Fig. 1. 

From the figure, it is found that the EERs of the 

ISO/IEC 19794-2 formats are slightly worse than that of 

the XYT format. The degradation of EERs of the 

Record format and Card format (Normal size) is only 

0.1%. This is because these formats have enough 

resolution in comparison with the XYT format. The 

degradation of EER of the Card format (Compact size), 

which has the small data size and low resolution, is 

0.77%. 

The characteristic of the FAR and FRR of each 

format with changing the threshold value is shown in 

Fig. 1. Comparison of EERs of each format. 

(Test Dataset 1) 
10 

9 

8 

%] 

7 

6 

5 

FAR, FRR [

4 

3 

2 

1 

0 

6 8 10 12 14 16 18 

100 

90 

80 

70 FAR FRR 

] [%60 FRR

50 

FAR, 40 

30 XYT 

20 Record 

10 Card(Normal) 

Card(Compact) 

0 

0 2 0 4 0 6 0 8 0 1 00 

Threshold value for matching score 

(a) Overall view 

Threshold value for matching score

(b) Magnified view around EER 

Fig. 2. Characteristic of the FAR and the FRR of each 

format with changing the threshold value. 

 (Test Dataset 1) 

Fig. 2. From the figure, it is found that only the FRR 

curve of the Card format (Compact size) becomes 

worse. This leads to the degradation of the EER of this 

format. The curves of other formats are very similar. 

From these results, the use of the ISO/IEC 19794-2 

formats has no problem from the viewpoint of the EER. 

4 Noticed Problems in Using the ISO/IEC 

19794-2 Formats 

In this chapter, noticed problems in applying the 

ISO/IEC 19794-2 formats to the MINDTCT and 

BOZORTH3 are discussed in detail. The problems 

under considerations are as follows; 

(1) Error of the minutiae coordinates and angle by the 

ISO/IEC 19794-2 formats. 

(2) No existence of the minutiae quality field in the 

Card formats. 

(3) Limitation of the number of minutiae. 

(4) No existence of the header field in the Card formats. 

(5) Limitation of the maximum size of fingerprint 

image in the Card format (Compact size). 

4.1 Error of the Coordinates and Angle by the 

ISO/IEC 19794-2 Formats 

In minutiae extraction process in the MINDTCT, the 

XY coordinates are recorded by pixel base. This 

process also truncates the angle of minutiae direction to 

32 directions, i.e., 11.25° resolution. After the 

truncation, the format conversion for minutiae data is 

done for each format. The conversion error, which 

degrades EER, is occurred in this process. 

4.1.1. Error in Converting Process to the ISO/IEC 

19794-2 Formats 

The conversion error in each format is as follows; 

(1) From the XYT format to the Record format

The XY coordinates has no error, because this 

resolution is same between the XYT format and Record 

format. However, the angle of minutiae direction has 

the conversion error caused by converting from 1° to 

1.40625°. 

(2) From the XYT format to the Card format (Normal 

size)

The XY coordinates has the conversion error caused 

by converting from 1 pixel unit to 0.01mm unit. The 

angle of minutiae direction also has the conversion error 

caused by converting from 1° to 1.40625°. 

(3) From the XYT format to the Card format (Compact 

size)

The XY coordinates has bigger conversion error 

caused by converting from 1 pixel unit to 0.1mm unit. 

The angle of minutiae direction also has bigger 

conversion error caused by converting from 1° to 

5.624°. In addition, the XY coordinate normalization 

process to avoid the limitation of the maximum size of 

fingerprint image in the Card format (Compact size) 

occurs serious error. 

4.1.2. Difference of the BOZORTH3 Matching 

Score of the XYT Format and ISO/IEC 19794-2 

Formats 

In this section, the difference between the BOZORTH3 

matching score of the XYT format and ISO/IEC 19794-

2 formats is cleared by the test dataset 2. The 

BOZORTH3 calculates matching score from two 

minutiae files. The score means similarity between two 

fingerprints. Relationship of the matching score using a 

pair of fingerprints between the XYT and ISO/IEC 

19794-2 formats is shown in Fig. 3. Relationship of the 

matching score using non-matched fingerprints is 

shown in Fig. 4. 

In these figures, the plots under y=x line shows the 

decrease of the matching score for the ISO/IEC19794-2 

formats. 

From Fig. 3, it is found that the distribution of the 

score of the Record format and Card format (Normal 

size) is not affected by this software. However, the Card 

format (Compact size) is greatly affected. This leads to 

the degradation of the FRR. The score of the Card 

format (Compact size) to non-matched fingerprints is 
160 

140 

120 

100 

80 

60 

40 Record 

20 Card(Normal) 

Card(Compact) 

0 

0 20 40 60 80 100 120 140 160

Matching score of the XYT format 

Matching score of the 

ISO/IEC19794-2 formats 25 

Matching score of the 

ISO/IEC19794-2 formats 20 

15 

10 

Record 5 Card(Normal) 

Card(Compact) 

0 

0 5 10 15 20 25 

Fig. 3. Relationship of the matching score using a pair 

minutiae in the header. From experimental results using 

200 fingerprints, there are 17 fingerprints which exceed 

255 minutiae. In this study, the selection process of the 

top quality 255 minutiae is implemented in the 

MINDTCT to avoid this problem. 

4.4 No Existence of the Header Field in the Card 

Formats 

The origin of Y coordinate in the XYT format is 

different from ISO/IEC 19794-2 formats as shown in 

Table 1. Thus, the BOZORTH3 has to convert the Y 

coordinate by using the vertical size of the fingerprint of fingerprints between the XYT format and ISO/IEC image after loading the minutiae file. However, the 19794-2 formats. (Test dataset 2) BOZORTH3 cannot acquire the vertical size of the 

fingerprint, because the Card formats do not have the 

header field. 

Matching score of the XYT format 

Fig. 4. Relationship of the matching score using nonIn this study, we give the vertical size manually in 

loading minutiae files to the BOZORTH3 in order to 

avoid this problem. For this problem, the whole system 

design from the minutiae extraction process to the 

matching score calculation process should be 

reconsidered as suitable to the ISO/IEC 19794-2 

formats. 

4.5 Limitation of the Maximum Size of 

Fingerprint Image in the Card Format (Compact 

matched fingerprints between the XYT format and Size) 

ISO/IEC 19794-2 formats. (Test dataset 2) 

As the resolution of X and Y coordinates is fixed in the 

Card formats, there is a limitation of the maximum size 

of fingerprint image. The limitation is 163.83 mm in the more changeable than that of the Card format (Normal 

size) as shown in Fig. 4. 

4.2 No Existence of the Minutiae Quality Field in 

the Card Formats 

Card format (Normal size), i.e. 0.01mm unit by 16383 

steps (14 bit), and 25.5 mm in the Card format 

(Compact size), i.e. 0.1mm unit by 255 steps (8 bit). 

As the image size of the Special Database 9 is width 

When the Card format is used, the selection of 150 

minutiae based on the quality is necessary in the 

MINDTCT. The reason is that this format does not have 

the minutiae quality field. The BOZORTH3 calculates 

matching score and feeds through 150 minutiae with 

higher quality order when the number of minutiae is 

over 150. In case of no quality information, the 

BOZORTH3 cannot use qualified 150 minutiae, and 

this causes the degradation of the score. In this study, 

the selection process of the top quality 150 minutiae is 

implemented in the MINDTCT to avoid this problem. 

From the experimental results by the Card format 

(Compact size) using the test dataset 2, the quality 

information improves the EER by 1%. 

4.3 Limitation of the Number of Minutiae 

The number of minutiae included in the ISO/IEC 

19794-2 formats is limited to 255. This limitation is 

caused by the 1 byte field length of the number of 

42.3 mm by height 39.0 mm, both of width and height 

exceed the limit of the Card format (Compact size) and 

overflowed. In this study, the X and Y coordinates of 

minutiae are normalized linearly by the actual 

fingerprint size in the MINDTCT and the BOZORTH3. 

However, this normalization process occurs the 

degradation of the coordinate’s resolution. 

The method of “X or Y coordinate extension for 

compact format” as specified in ISO/IEC 19785 Data 

Object can avoid this problem. However, this method 

does not support in the case of both of X and Y 

overflowing. It is necessary to trim the examined area 

from the fingerprint image. 

5 Conclusion 

In this study, the MINDTCT and BOZORTH3 were 

modified to accept the data based on ISO/IEC 19794-2 

formats, and used for automated fingerprint 

authentication experiment. The problems and influence 
 

on the authentication accuracy of the ISO/IEC 19794-2 

formats are also examined. 

From experimental results, the EERs of the ISO/IEC 

19794-2 formats become slightly worse than that of the 

XYT format. The degradation of EERs of the Record 

format, Card format (Normal size), and Card format 

(Compact size) are 0.1%, 0.1%, and 0.77% respectively. 

This result show that the use of the ISO/IEC 19794-2 

formats in commonly available software is accepted 

from the viewpoint of the EER. The problems and 

influence in applying the ISO/IEC 19794-2 formats 

may be solved if the whole system design from the 

minutiae extraction process to the matching score 

calculation process is reconfigured as suitable to the 

ISO/IEC 19794-2 formats. 

Acknowledgments. This study was supported by the 

standardization committee of New Media Development 

Association supported by FY2008 METI research and 

development project for standards and conformity assessment. 

References 

1. “ISO/IEC19794-2, 2005 Information technology – 

biometric data interchange formats – Part 2: Finger 

minutiae data”, ISO (2005) 

2. NIST, “User’s guide to NIST Biometric Image Software 

(NBIS)” 

3. C. I. Watson, “NIST special database 9, Mated fingerprint 

card pairs”, NIST (1993)