Portable Biometrics Workstation: Session Interface 

Jeff Young 

February 1, 2005 

February 19, 2005 

Jeff Young 

For: 

National Institute of Standards and Technology 

Jean Scholtz 

Address inquiries to: Jean Scholtz 

Phone: (301) 975-2520 

Email: jean.scholtz@nist.gov 

Address: 100 Bureau Dr, MS 8940, Gaithersburg, MD 20899 

1 
Executive Summary 

The portable biometric workstation is being developed as a means of creating a database of 

biometric information. The workstation will consist of nine (9) digital cameras that will capture a set 

of face photographs from different angles. Two (2) different fingerprint scanners will be used to 

collect digital fingerprints. Irises will be digitally recorded using an iris scanner. Each step 

(photographs, fingerprinting, and iris scanning) will be accomplished twice for the database in a 

single session. Six (6) months after the first data capture a second data capture will occur. This 

will create a database of biometrics taken at two points in time from the same person. The goal is 

to collect 10,000 sets of data. An operator will use the session interface to direct subjects through 

the workstation. The interface must clearly indicate what task is being accomplished as well as 

any specific requirements of the individual tasks. 

In order to collect 10,000 complete sets of biometrics, we estimate using the workstation at least 

25,000 times. In order to minimize the time, both for operators and the biometric subjects, it is 

critical that the usability of the workstation be maximized. 

To test the usability of the session interface an interactive prototype was created. Participants 

were asked to play the role of the operator while developers played the roles of the assistant and 

the user (the person having biometric data collected). All the biometric data “collected” in the 

prototype was fake data. This was explained to the participants prior to the scenarios. There were 

three (3) scenarios; in the first scenario everything was normal and in working condition, in the 

second scenario two of the scanners were offline due to errors, and in the third scenario everything 

appeared normal but there were three scanning errors during the walkthrough. The scenarios 

were presented in the same order for all participants. After each scenario the participants were 

given a brief six-item questionnaire with space to provide feedback about the interface. 

There were eight (8) participants, five (5) males and three (3) females. All were NIST employees 

at the time of the experiment. 

The overall average time per scenario was 208 seconds. For the 1st and 3rd scenarios (with all 

tasks available) the average time was 239 seconds. The face photos took an average 28 

seconds, fingerprints averaged 37 seconds per set (LH/RH and thumbs), and iris scans averaged 

17 seconds. NOTE: These numbers do not take into consideration the actual “true” equipment 

timing. These numbers are based on 1.6 second simulated scan/display times. 

There were few errors committed during the testing. Most of the errors that did occur were based 

around incorrect prompting. There were fewer errors committed as the session progressed, even 

though scenarios two and three had various sensor and image errors. 

The collection times (photos, fingerprints, iris scans) stayed fairly constant across 

participants/scenarios, which implies that the timesavings between the scenarios are mostly due to 

an increased understanding of the procedure and tasks. 

Almost all of the participants rated the interface and its components as easy to use. Even those 

who found it difficult in the first scenario rated it easier to use in the subsequent scenarios. 

Observations of operator behavior suggest that the assistant may be an unnecessary role. 

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Introduction 

Full Product Description 

The portable biometric workstation is being developed as a means of creating a database of 

biometric information. The workstation will consist of nine (9) digital cameras that will capture a set 

of face photographs from different angles. Two (2) different fingerprint scanners will be used to 

collect digital fingerprints. Irises will be digitally recorded using an iris scanner. Each step 

(photographs, fingerprinting, and iris scanning) will be accomplished twice for the database in a 

single session. There is also an operator workstation, which will guide the flow through the 

biometric workstation and make sure the biometric data is properly captured. The operator 

workstation is also referred to as the session interface. 

Nine Olympus Camedia C-5050 digital cameras were setup to capture the face photographs. One 

LS2 and ID500 scanners were setup to capture fingerprints. The OKI EQ5051A was setup to 

capture iris scans. None of the equipment was connected during the experiment, as we were only 

interested in testing the session interface. All biometric data “captured” by the session interface 

was fake data. This was explained to the participants in advance. 

TSA agents will be using this workstation for the collection of a massive amount of biometric data. 

Test Objectives 

The experiment was conducted to assess how long each collection step took in the session 

interface and to determine if the interface facilitated the flow of the workstation. We also looked for 

any physical problems associated with the flow of the workstation and how well the session 

interface supported the operator during the data collection. 

Method 

Participants 

Eight participants were tested: 5 males and 3 females. 

All participants were NIST employees. They had basic computer knowledge but were not 

knowledgeable in biometrics. 

Participants were solicited by e-mail and word of mouth. There were no key characteristics 

considered in the selection of participants. 

As they all work at NIST, there is the possibility that the participants for this test had more 

computer knowledge than the average user population for this interface. 

For the duration of this report, participants will be referred to as “operators.” The operators 

interacted with three developers during the experiment. One developer was an observer who 

administered the experiment and answered any questions the operator had. A second developer 

played the role of the “user,” who was the person having their biometric data collected. The third 

developer acted as the “assistant,” who helped the operator and positioned the user for each 

collection sequence (photographs, fingerprinting, and iris scanning). 

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Context of Product Use in the Test 

During the actual biometric collection in the field, there will probably be several people (users) waiting in 

line to use the workstation. There will also be a second assistant using a separate workstation to register 

those users waiting in line. The possible confusion caused by these interactions was not addressed in 

the experiment. Also, our users and assistants were more knowledgeable about the system than actual 

users will be. 

Tasks 

The operators were asked to use the session interface to collect biometric data from a user. In 

doing this, they were using the task flow presented in the session interface, ensuring that the 

proper data was collected and that the data was acceptable. They also needed to direct the 

assistant to position the user correctly for each type of biometric collection. 

This task was selected to evaluate the usability of the interface and gather an approximation of the 

time needed to complete the collection procedures. 

Completion of the task was achieved after photo, fingerprint, and iris scans were collected. 

Test Facility 

The test was conducted in a biometrics lab. The spaced used was about 12’ x 8’. The operator 

sat on one side of a table while the fingerprint scanners were placed on the other side, facing out. 

The digital camera array was positioned to the left and perpendicular to the operator. The iris 

scanner was positioned directly across the room from the operator. 

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Participant’s Computing Environment 

The computer used in the experiment was a Dell Precision 360 with a Pentium 4 processor 

running Windows NT. 

Display Devices 

A ViewSonic VG700b 17” flat LCD monitor was used. Resolution was 1024 x 768 and 32-bit 

color was used. 

Manual Input Devices 

Standard mouse 

Test Administrator Tools 

A paper-based questionnaire was used to elicit usability feedback and suggestions. The 

questionnaire had six (6) five-point Likert scale statements with room for comments after each 

statement. There was room to comment on the interface as a whole at the end of the 

questionnaire. 

The computer running the session interface had Camtasia running in the background. Camtasia 

is a commercially available program that captures the video of the computer screen and saves it 

as an AVI file. A microphone was also used with Camtasia to capture any comments the operator 

may have had. 

An observer made notes and collected timing data. 

Experimental Design 

The operators were asked to step through the biometric collection process using the session 

interface. After being introduced to the assistant and user, the operators did three sessions of 

biometric data collection with the interface. 

During the first session everything was normal in the interface and there were no errors. 

During the second session, two of the scanners were offline and the operator had to modify the 

normal sequence based on the notification of this in the user interface. The third session had 

three separate image errors that the operator had to deal with. All operators did these sessions 

in the same order. 

Procedure 

The participants were greeted as they walked into the lab and handed an Informed Consent form 

to fill out. They were also handed a more detailed participant write-up. The participants were 

asked to play the role of “operator” both verbally and in the physical write-up. They were given a 

manual for the session interface and a brief explanation of its function. The assistant and user 

were introduced, and the operator then collected biometric data (fake data) from the user. This 

collection process was repeated three times with a questionnaire after each session. At the end of 

the experiment the operator was thanked for his/her participation, given a copy of the Informed 

Consent form, and allowed to leave. 

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Error collection (captured by the observer) - Errors were defined as the following: 

1. Incorrectly or forgetting to prompt the assistant 

2. Skipping a step that can be done 

3. Accepting a corrupted image 

The beginning of a task was defined as the session interface highlighting that task; the end of a 

task was defined as the session interface highlighting the next task. 

There were no time limits on tasks. 

The operators were free to ask questions during the experiment. Calculated task times do not 

include the time used for questions. Operators were told to prompt the assistant to position the 

user, but there were no set rules on direct interaction with the user. This was because part of the 

experiment was to see how these interactions played out. The prompts from the operator to the 

assistant were displayed in the user interface. 

There were three people who interacted with the operator: the observer, who took notes, ran 

Camtasia, and answered questions; the user, who had fake data collected from him/her; and the 

assistant, who positioned the user after prompting from the operator. 

For a few of the tests there was an extra observer taking notes in the background. 

All time was volunteered from the participants and they were not paid. 

Participant General Instructions 

The operators had the following general instructions: 

This study is being performed to test the usability of an operator interface that will be used to 

help collect data for a biometric workstation. You will be asked to act as an operator at the 

biometric workstation. Biometric workstation developers will play the roles of assistants and 

subjects. Using the operator interface, you will collect biometric data from the developers 

acting as the subjects in the experiment. You will be given training on the use of the operator 

interface, and then the actual experiment will begin. 

During the experiment your comments (about the interface and to the assistants) and 

interactions with the interface will be recorded. There will be at least one investigator taking 

notes and a video of the experiment will be recorded. There will be a short questionnaire for 

you to fill out as well. 

Participant Task Instructions 

The operators had the following instructions during the beginning of the experiment: 

This study is being performed to test the usability of an operator interface that will be used to 

help collect data for a biometric workstation. You will be asked to act as an operator at the 

biometric workstation. Two other people will play the roles of assistant and user. Using the 

operator interface, you will collect biometric data from the user in the experiment. You will ask 

6 
your assistant to position the user for each task. When your assistant is ready he/she will let 

you know. 

Your assistant will have had training on the collection equipment in the workstation, but this 

will be the first time he/she has been exposed to the biometric workstation. You should 

prompt the assistant on the task order and what he/she needs to do. 

The operator interface you will be using is a prototype. The data collected will be fake data 

and not collected in real time. Therefore, the photos may not be of the person acting as the 

subject, however this should not interfere with the experiment as we would like you to focus on 

the interface and not the specific data being collected. 

The photos will be taken from nine (9) different angles and displayed together. As long as the 

photos represent the subject as he/she is supposed to look, you should accept them. It does 

not matter if the photos are not completely centered as long as the face is visible. 

When taking the fingerprint and iris scans, the data captured will appear briefly in the Sensor 

Feedback window and then disappear. This is because the equipment automatically accepts 

correct images. If there is an image problem, the interface will alert you. 

You will be given a manual describing the operator interface. You are free to ask questions 

about the workstation and the collection procedure. You may also ask for help during the 

experiment if necessary. When you are ready to start the experiment, please let us know. 

Thank you for your participation. 

Usability Metrics 

Effectiveness was measured by counting the number of errors (see error definition under 

“Procedure” section). 

Efficiency was measured using the time to complete each session and time to complete each task 

(face photos, fingerprints, and iris scans). 

User satisfaction was measured by using the results of the questionnaires (see Appendix A for 

questionnaire). 

Results 

Data Analysis 

Much of the data was taken from the timing of the tasks. The participant comments also figured 

prominently in the re-design of the session interface. 

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Presentation of the Results 

Performance Results 

Effectiveness: Session 1 

User # Incorrect Prompting Skipping a doable task Accepting bad image 

Participant 1 

Participant 2 

Participant 3 1 

Participant 4 2 

Participant 5 

Participant 6 1 

Participant 7 1 

Participant 8 

Total 5 

Effectiveness: Session 2 

User # Incorrect Prompting Skipping a doable task Accepting bad image 

Participant 1 1 

Participant 2 2 

Participant 3 

Participant 4 

Participant 5 1 

Participant 6 

Participant 7 

Participant 8 1 

Total 2 3 

Effectiveness: Session 3 

User # Incorrect Prompting Skipping a doable task Accepting bad image 

Participant 1 

Participant 2 

Participant 3 1 

Participant 4 1 

Participant 5 

Participant 6 

Participant 7 

Participant 8 1 

Total 1 2 

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There were few errors committed during the testing. Most of the errors that did occur were based 

around incorrect prompting. There were fewer errors committed as the session progressed, even 

though scenarios two and three had various sensor and image errors. 

Skipping a doable task and accepting a bad image were scenario specific errors (scenarios 2 and 

3 respectively). The doable tasks that were skipped in scenario 2 were due to confusion with the 

prompts, which didn’t skip with the tasks correctly. The two bad images that were accepted were 

face photographs that had one image corrupted (out of a grid of the nine photos taken). This may 

have been due to the size and placement of the photos relative to the rest of the interface. The 

photo grid was displayed in the upper left-hand corner. It is our belief that displaying the photos 

larger and in the middle of the screen will draw the operator’s focus more effectively. 

Efficiency (in seconds – rounded to nearest second) 

User # Scenario 1 Scenario 2 Scenario 3 Face photos Fingerprints Iris scans 

Participant 1 250* 131* 239 48 36 7 

Participant 2 379* 304 37 50 22 

Participant 3 255 98 202 20 36 19 

Participant 4 147* 116* 169 24 20 9 

Participant 5 267* 188 18 38 18 

Participant 6 343 136 220 40 40 16 

Participant 7 234 124 190 22 34 18 

Participant 8 220 143* 217 22 37 18 

Mean 262 125 224 29 37 17 

* Some sessions had missing time data. For the cells that were missing data, the average of a 

particular task was used to create the estimated session time. The blank cells are scenarios that 

did not have task times captured. 

Face Avg Fingerprint Avg Iris Avg Overall Avg 

Scenario 1 36 40 17 262 

Scenario 2 24 39 125 

Scenario 3 25 33 17 224 

Mean 29 37 17 208 

The average time per scenario appears to decrease as the scenarios progress. Scenario 2 is 

noticeably shorter in duration because two of the sensors weren’t working during that scenario. 

However, combined with the error data it appears that repetition speeds up the process, and Scenario 

3 is noticeably faster than Scenario 1 even with the image errors introduced in Scenario 3 (both 

scenarios had all the sensors in working order). Hence we infer that as the operator gets more 

experience the time will be shorter. However, our users were knowledgeable and cooperative. With 

naïve users the flow may not be as smooth. 

The face photos, fingerprint scans, and iris scans all had reasonable average times, but it must be 

noted that these numbers do not take into consideration the actual “true” equipment timing. These 

averages are based on a 1.6 second simulated scan/display time. The collection times (photos, 

fingerprints, iris scans) stayed fairly constant across participants/scenarios, which implies that the 

timesavings between the scenarios are mostly due to an increased understanding of the procedure 

9 
 

 

and tasks. The participants were given only a brief overview of the interface and it’s functioning before 

using it. Operators in the field will have more knowledge of the procedures, but this early testing 

indicates that the training and learning curve probably won’t be too steep. 

Satisfaction Results 

Satisfaction: Questionnaire Responses (see Appendix A for questionnaire) 

 1 = Easy; 5 = Hard 

User # Q 1 Q 2 Q 3 Q 4 Q 5 Q 6 

Participant 1 

Session 1 2 4 4 2 3 2 

Session 2 2 4 2 2 2 2 

Session 3 1 3 2 2 2 2 

Participant 2 

Session 1 1 2 3 1 1 1 

Session 2 5 1 3 4 3 

Session 3 1 1 1 1 1 

Participant 3 

Session 1 1 1 2 1 1 1 

Session 2 1 1 1 1 1 1 

Session 3 1 1 1 1 1 1 

Participant 4 

Session 1 1 1 1 3 1 

Session 2 2 1 1 1 3 1 

Session 3 1 1 1 1 3 1 

Participant 5 

Session 1 1 1 1 1 1 

Session 2 1 1 1 1 1 

Session 3 1 1 1 1 1 1 

Participant 6 

Session 1 1 1 1 1 2 2 

Session 2 2 1 1 1 2 2 

Session 3 1 1 1 1 1 2 

Participant 7 

Session 1 4 5 1 1 3 2 

Session 2 1 5 3 1 3 2 

Session 3 2 3 2 2 3 2 

Participant 8 

Session 1 1 1 1 1 3 3 

Session 2 2 1 1 5 2 

Session 3 1 1 1 1 2 2 

Mean 1.55 2.00 1.46 1.25 2.17 1.63 

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The interface used was fairly straight forward (see Appendix B), so the results are not surprising. 

Almost all of the participants rated the interface and its components as easy to use, and it should 

be noted that satisfaction generally increased with use. There were also several comments and 

suggestions to make the interface better. A couple of the more frequent suggestions involved 

positioning the prompts in closer proximity to the task list and making it clearer when a user needs 

to remove his or her glasses (for a photo or iris scan). 

After observing several participants it became apparent that the operator talked more directly with 

the user after the first set of fingerprints had been taken. At that point several operators ignored 

the assistant and told the user directly what to do. This raises the question of whether an assistant 

is necessary (though it must be noted that our users knew more about the system than the 

average user in the field will). More testing needs to be done to see if the assistant can be 

removed with little negative effect. Removing the assistant would save training time and money 

during deployment of the workstation and should be carefully considered. 

There is also the question of how long an operator can use the interface without a decrease in 

effectiveness or efficiency. This was not tested here but needs to be examined. This needs to 

take into consideration concentration issues as well as the possibility of boredom. Removing the 

assistant may not only save money but also engage the operator more in the data collection. It 

must be determined how to efficiently rotate operators between the registration interface and the 

session interface during the course of a day, allowing some down time and a change of task. 

Status 

Currently the session interface has been revamped with consideration to the comments and 

observations made during the testing. Future work includes testing the workstation without an 

assistant. There also needs to be some testing done with naive users to better estimate the time 

required to gather biometric data. Long term testing needs to be done to determine timing 

platuaus and the length of time an operator can use the interface before effectiveness and 

efficiency decrease. 

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Appendix A – Interface Questionnarie 

Questionnaire Subject________ Iteration___ 

With relation to the interface you just used, please circle the number that corresponds to your 

experience. Below each question is a space for you to comment on your specific experience. 

1. The procedure for collecting the face photo was 

 Very easy Very difficult 

to conduct 1 2 3 4 5 to conduct 

Comments:________________________________________________________ 

2. Asking the subject to remove his glasses for the second photo was 

 Very easy Very difficult 

to remember 1 2 3 4 5 to remember 

Comments:________________________________________________________ 

3. Prompting the assistant on how to maneuver the subject was 

 Very easy Very difficult 

to remember 1 2 3 4 5 to remember 

Comments:________________________________________________________ 

4. The fingerprints were 

 Very easy Very difficult 

to obtain 1 2 3 4 5 to obtain 

Comments:________________________________________________________ 

5. Overall, the interface was 

 Very easy Very difficult 

to understand 1 2 3 4 5 to understand 

Comments:________________________________________________________ 

6. The timing of the tasks was 

 Very Fast 1 2 3 4 5 Very Slow 

Comments:________________________________________________________ 

What did you dislike about the interface? How would you change the interface to make it better? 

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Appendix B – Screenshot of Operator Interface 

13