Visualizing Ergonomic Data of Industrial Work Processes: A Design

Study

Walentin Heft

, Linda Pfeiffer

and Paul Rosenthal

Faculty of Computer Science, Chemnitz University of Technology, Straße der Nationen 62, Chemnitz, Germany

Faculty of Humanities, Chemnitz University of Technology, Th

uringer Weg 11, Chemnitz, Germany

Keywords:

Information Visualization, Ergonomics, HCI, Evaluation.

Abstract:

Ergonomics deals with the analysis and design of work processes. To identify ergonomically critical situations,

appropriate evaluation options have to be developed to enable an efﬁcient analysis process. Nowadays, such

analyses are typically carried out with the help of digital models of the surrounding area and virtual humans.

These produce a multitude of geo-referenced and time-oriented data. We present a design study on how

to visualize this data to support the ergonomically analysis process optimally. As consequence of a thorough

requirements analysis and design process, we propose a novel interactive visualization which provides the user

an overview of ergonomically critical situations and their causes. Simultaneously, the user obtains the main

stress factors in a compressed form by a glyph-based visual design. Final expert interviews and a usability

study depict the utility of the proposed visualization tool.

1 INTRODUCTION

For a few years, the scientiﬁc institute of the Ger-

man health insurance AOK (WIdO) (Zok, 2010) per-

formed an employee survey in 147 German compa-

nies about health disorders and workload. In total,

more than 28,000 people were surveyed in companies

with a size between 35 and 2,252 employees. When

asked, “What do you ﬁnd more important for your

health” 55 percent of the respondents answered (after

enough sleep and a balanced diet) that healthy work-

ing conditions are decisive. Many employees suffer

under heavy physical work. This includes particularly

heavy loads as “lift and carry”. Thus, there is gener-

ally a need for action to improve the employment sit-

uation in the companies. Especially ergonomists deal

with the elimination of bad work situations. They ex-

amine the work, take measurements, and analyze the

data obtained. According to the analysis they present

their ﬁndings to third parties, for example to the man-

agement.

In this regard, studies of longer periods (an entire

shift or several working cycles) can lead to a huge

amount of data and complex structures. Thus, the

evaluation of the values obtained and the presentation

towards the authorities concerned can be very chal-

lenging. However, satisfactory visualizations are cur-

rently still rare and often limited to simple line or bar

charts. In a previous publication (Heft et al., 2015),

we presented an user-interaction concept and ﬁrst pre-

liminary designs to visualize ergonomic data. In this

paper, we present a thorough design study and inves-

tigate how an interactive visualization could lead to

a facilitation of the evaluation work of ergonomists.

At ﬁrst, we performed a requirements analysis in co-

operation with real ergonomists and with the help of

everyday use cases from real work places, see Sec-

tion 2. Afterwards, we performed an iterative design

process on basis of the gathered requirements, lead-

ing to a working prototype, see Section 5. Finally,

we conducted a user study with different usergroups

(ergonomists and laymen) to valuate the usability and

beneﬁt of this interactive visualization, see Section 6.

2 REQUIREMENT ANALYSIS

For obtaining a human-centered visual design, a de-

scription of user context and user requirements has to

be made. In order to analyze the user context it is nec-

essary to record user characteristics, work tasks, and

framework conditions.

We obtained these insights by means of work-

shops (in two German companies) with ergonomists

and occupational health and safety practitioners (in

total seven experts). We used the method “focus

274

Heft W., Pfeiffer L. and Rosenthal P.

Visualizing Ergonomic Data of Industrial Work Processes: A Design Study.

DOI: 10.5220/0006175202740282

In Proceedings of the 12th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications (VISIGRAPP 2017), pages 274-282

ISBN: 978-989-758-228-8

group” (Courage and Baxter, 2005, pp. 25ff), i.e., we

presented our questions to groups of experts. We dis-

cussed the steps of the requirements analysis in detail

in Heft et al. (Heft et al., 2015).

We summarize its results below:

The user’s task

The ergonomists have the task of analyzing and

improving the technical, organizational, and so-

cial conditions of work processes. For this pur-

pose data needs to be collected, evaluated, and

transferred into adequate solutions. Furthermore,

their outcomes will be presented to the manage-

ment or to the worker.

Requirements

• an easy-to use program

– interactive explanations on all displayed ele-

ments

– detailed information about the analyses should

be easily obtainable (if required)

• intuitive and sustainable data representation

– understandable to non-experts

– fast overview of all ergonomic problems over

time

– falling above/below limit values should be vis-

ible at a glance

– color coding, instead of tabular form

– simple images for presentation

– video to show the workers the work ﬂow

• hardware requirements

– executable on standard PCs

Data to be visualized

• posture

• time of occurrence

• duration of a ergonomically critical situation

• score of the different evaluation methods

• reasons for an issue, such as the weight of a

carried object

• additional variables, for instance, the body joint

angles as well as their limit values

3 STATE OF THE ART

The presentation of ergonomic results is often bound

to lists, simple graphical dialogs, and graphs. The

most popular representations of ergonomic reports for

RULA (McAtamney and Nigel Corlett, 1993) origi-

nate from the digital human models (DHM) “Human

Builder” (Dassault Syst

emes) and “Jack” (Siemens).

In either case, they based on a straightforward tabular

form. Their views show the ratings of the individual

body parts (e.g. for the upper arm, neck, and legs), the

force and load values, and the total number of points

of the pose (incl. a color coding in the trafﬁc light

scheme). “Dynamicus” (Institut f

ur Mechatronik e.V.,

2016) is an example of an ergonomic report, which

represent the results of the EAWS method (Schaub

et al., 2013) in a DHM. Here, the representation of

the time component is incorporated. It indicate the

pose through a rotatable DHM, duration, partial eval-

uations, and the total score of the analysis, for exam-

ple. Bad poses are notiﬁed over a gantt chart.

The programs, however, are not fully capable to

comply with the desired user requirements. First,

there is no way to change the depth of analysis. On

the other hand, only a static pose can be displayed, in-

stead of a complete overview of all problems. Visual

analysis of the data by zoom and ﬁlter mechanisms is

often not supported. Moreover, the problems are al-

ways displayed for a single method of analysis. This

means, that possible interrelated causes cannot be per-

ceived.

4 RELATED WORK

Since time-oriented data is relevant in many practical

situations, the visualization of such data is ubiquitous.

Many recent work exists (Aigner et al., 2011), (Silva

and Catarci, 2000), (Tominski and Aigner, 2015).

However, visualizations in digital human models for

showing critical ergonomic situations or illustrating

time-oriented processes are very limited.

The concept of timelines for time-oriented data is

used in LifeLines (Plaisant et al., 1996). LifeLines

was developed to create an overview about certain

events in the life of a person. Because of the pres-

ences of all import information at one stage, the doc-

tors can provide a better prognosis about the medical

condition.

However, an overview for a mass of data can

quickly lead to confusion. LifeFlow (Wongsupha-

sawat et al., 2011) delivers a possibility to counter-

act this circumstance with event sequences (series of

temporal distinct and consecutive events). In connec-

tion to the aforesaid work (LifeLines), individual data

records can be displayed with much more detail.

In order to perform a performance analysis in real-

time sports events (e.g., rugby or football), videos are

annotated by analyst teams. However, this leads to

a large amount of statistics or tables with many data

records. It would be almost impossible for a trainer to

capture this data in real time. Thus, important details

could easily be overlooked. Matchpad (Legg et al.,

Visualizing Ergonomic Data of Industrial Work Processes: A Design Study

275

2012) provides a solution by means of a glyph-based

overview visualization. Kicks, a line out, or referee

events are displayed on a time scale in real time.

Timelines are mostly used for the visualization of

time-oriented data. These often begin on the left side

and run horizontally to the right side (as LifeLines or

programs for editing and displaying video and audio

ﬁles). However, this is not always necessary. For ex-

ample the VisRuption project (Rosenthal et al., 2013)

facilitates timelines that run from the bottom to the

top.

The above listed publications provide approaches

and ideas for this work. However none of the exist-

ing work corresponds to the user requirements of an

interactive visualization for an overview display of er-

gonomic problems.

5 DESIGN PROCESS

The designing of the workable visualization was done

on basis of the user requirements and iterative proto-

typing. During the implementation, the current state

was discussed with the experts in several meetings.

Some errors in the design and programming were dis-

covered and subsequently removed. New enhance-

ments were proposed and integrated into the program.

C++ and Qt was used to create the software.

The functional parts of the GUI are shown in Fig-

ure 1. It can be divided into two main sections. The

upper part provides a quick overview and is divided

into three levels, such as the display of selected crit-

ical situations as pictograms, the total scores of se-

lected problems per analysis method, and a timeline

with all ergonomic problems. The lower part provides

opportunities for detailed analysis with a video-view

and a display, which may include detailed informa-

tion about calculations and other results. A help but-

ton is located at the right edge of each level. The help

describes the elements, and the interaction of the re-

spective level.

5.1 Pictogram Level

The pictograms of the ﬁve currently selected er-

gonomically critical situations are shown on the ﬁrst

level (see Fig. 1, pictogram level). The presentation

symbolizes bad poses, impairments by noise, etc. The

problem can be selected by a click on a pictogram.

This selection leads to two reactions, an optical and a

functional.

Optical: The problem is shown with a gray back-

ground (see Fig. 1, the centrally positioned prob-

lem). The background stretches over the correspond-

ing evaluation points (see Sec. 5.2) of the selected

problem and ends at the problem position on the time-

line (see Sec. 5.3). This is intended to help the user to

keep the data of a critical situation, across all levels,

in mind.

Functional: By selecting a problem, the appropriate

video sequence shows the current problem in a loop

(see Sec. 5.4). In addition, the corresponding calcu-

lation details are displayed. Additional information

can be attached to the right of a pictogram. They are

intended to provide information about the reasons for

a poor assessment, such as a carried (heavy) weight

or an excessively bent body. Besides the symbolic

representation, the user receives the exact values via

tooltip. Directly below a pictogram, there is a stop-

watch symbol and the duration of a single action. The

distance line between two pictograms is labeled with

the duration from the end of an action to the begin-

ning of the following problem. If more than ﬁve prob-

lems are selected in the timeline, the arrows on the left

and right of the pictogram bar allow a navigation. By

means of a mouse click, additional problems can be

displayed. There are two arrows on each side: A sim-

ple arrow is used to move one problem at a time, the

double arrow shows the next ﬁve problems. The for-

mer makes it possible to compare problems that occur

in succession but are not presented in the view. The

double arrow allows faster selection of all selected

problems, so the next ﬁve are displayed. Between the

two arrows, the number of the following resp. preced-

ing cases is given.

5.2 Assessment Level

On the second level (see Fig. 1, assessment level),

the total score points for each analysis method (e.g.

RULA, EAWS, noise and climate) are shown for the

displayed ﬁve problems. The results are structured

in tabular form. Each row contains the values of a

analysis method. The method is indicated at the be-

ginning of each row. This allows a comparison of

all values over time. The ﬁrst column of a table (lo-

cated below a pictogram) indicates the severity of a

problem by color coding. The red color symbolizes a

very high-risk problem and improvements should be

made immediately. Orange represents an intermedi-

ate risk and changes should be made soon. A low

risk is expressed by yellow. If there is no risk, white

is used for the corresponding evaluation method. This

was implemented in contrast to the original color cod-

ing (green), due to the reasons mentioned in Section

5.5. A click on the color ﬁeld selects the problem and

marks it with a gray background as explained in the

description of pictogram level. Furthermore, it will

IVAPP 2017 - International Conference on Information Visualization Theory and Applications

276

Figure 1: The implemented interactive visualization with a chosen area on the timeline and a selected problem. The pictogram

level symbolizes the reasons of the problems. The assessment level shows the overall scores of the corresponding analysis.

The severity of the problem is color coded. The third level (timeline) contains selectable bars. The bars starts at the position

relative to the real time. The length corresponds to the duration of the problem and the color to its severity. The detail view

encloses a video and space for further informations.

open the corresponding tab in the detailed view (see

Sec. 5.4). For example, if the user clicks on a color

ﬁeld in the “noise” row, the noise tab is automatically

selected in the detail view. The second column of a

table contains the total points of an analysis.

5.3 Timeline

A timeline is depicted on the third level (see Fig. 1,

timeline). The colored bars symbolize the ergonomic

problems. The beginning of a bar starts at the posi-

tion relative to the real time. The length corresponds

to the duration of the problem and the color to its

severity. The problem can be selected by a click on

the bar. This displays the corresponding details in the

other levels (pictogram, assessment, detail). The crit-

ical cases are listed in rows for each analysis method.

Below the timeline is a slider. At the right end, the

total time is indicated in seconds. Two controllers

are located on the slider. A certain time range can

be chosen by setting the respective controller to the

desired position. The current position is located di-

rectly below the controllers. A vertical auxiliary line

is located on each controller over the entire height of

the timeline. This allows a precise positioning of the

controllers (e.g., directly before or after a problem).

The start time of a problem can also be determined

via tooltip. If a time period has been selected, the in-

side area is zoomed in. The bars and the time are in-

creased in proportion. All problems before and after

the selected time period are collapsed by compressing

the time and the bars. In order to highlight the area of

interest, the external problem areas are grayed out.

5.4 Detail Level

On the detailed view (see Fig. 1, detail level) there

is a video and a detail representation. In the nor-

mal state, the video shows automatically the sequence

of the currently selected problem in a loop. The

“FullScreen” button opens the video in full screen.

The “Esc” key or a double-click terminates the full

Visualizing Ergonomic Data of Industrial Work Processes: A Design Study

277

screen mode. Pressing the stop button closes the

video and sets it to the beginning. By pressing the

play button, the entire workﬂow can be viewed from

start to end. A slider below the video shows the

current position/time (as well as the total time) and

allows the user a navigation (forward / backward)

within the displayed animation. The contents of the

detailed view are not implemented in this work, but

are intended to provide the exact values for each

analysis. This means that the intermediate results

(which contribute to the overall score of each valu-

ation method) can be selected and displayed via the

already available tabs.

5.5 Color Selection

In the ﬁeld of ergonomics, the results are preferably

visualized in the trafﬁc light scheme (green, yellow,

occasionally additional orange, and red). First, it

may be useful to maintain the domains-speciﬁc design

guidelines in terms of the recognition value. How-

ever, we avoided a “red-green”-visualization for two

reasons:

1. Red-green weakness: About eight percent of the

European males are affected. The corresponding

colors cannot be perceived correctly.

2. Show only problems: The core task of the er-

gonomists is to examine the most dangerous activ-

ities and to improve their execution. Using green

in the visualization for uncritical situations can

leads to an overloading of the overview and a dis-

traction from interesting points.

Instead, we have chosen to indicate the problems with

a color coding that changes from yellow to red. All

non-problematic time points are colorless or white.

6 EVALUATION

As the ﬁnal step of our design study, we have evalu-

ated the prototype. In the following, we describe the

procedure and the results of our user study.

6.1 Methodology

6.1.1 Study Design

We decided to do a qualitative evaluation. This has

two advantages. On the one hand the users’ thoughts

and feelings can be assessed in more detail. This is

an important quality in order to understand the users

experience. On the other hand is this approach more

explorative. This is an important quality, because it is

impossible to know about the speciﬁc problems that

will occur during the study in advance. To ensure that

the functionality of the prototype was discovered by

the test persons, a set of tasks was given to them. They

were told to follow the “think aloud” approach during

the test of the visualization, in order to get a deeper

understanding of their thoughts and feelings. Thus,

we had the chance to understand the users experience

and the reasons for their problems.

We used the standard norm of “EN ISO 9241-110”

for our evaluation, which deﬁnes aspects of good dia-

logues (DIN, 2010):

• suitability for the task,

• suitability for learning,

• suitability for individualization,

• conformity with user expectations,

• self descriptiveness,

• controllability, and

• error tolerance.

These aspects, as well as the readability, may give

hints on potential sources of problems. Thus, we

wanted to have another measurement for these as-

pects and introduced an additional questionnaire. The

evaluation was complemented by an interview, that

gave the chance to get detailed information on spe-

ciﬁc problems. The prototype was tested in a labora-

tory study. This allows a calibration of the soft- and

hardware and a controlled surroundings. Observa-

tions with “pen and paper” and video recording were

done.

6.1.2 Participants

According to Nielsen (Nielsen, 2016) 5 participants

are sufﬁcient for a qualitative study. Additional par-

ticipants would encounter almost the same usability

problems. Several groups of highly distinct users

need 3-4 users from each category. This study in-

cluded two categories of users:

• 3 experts on ergonomics

• 4 non-experts

The group of experts was chosen in order to ensure

the relevance of the visualization in practice and its

suitability to the ergonomists. On the other hand, the

tool should also be intuitively comprehensible to non-

experts, like managers or small companies, that have

no ergonomist.

6.1.3 Test Setup

The study took place in a separated room. The ob-

server and the participant were present. The proto-

IVAPP 2017 - International Conference on Information Visualization Theory and Applications

278

type ran on a standard laptop (Windows). The vi-

sualization was shown on a 22” display. Interaction

devices have been a standard mouse and keyboard.

Each session lasted at most one hour and consisted of

a brieﬁng, the usability test, answering the question-

naire, and an interview.

6.1.4 Brieﬁng

The brieﬁng consisted of an information about the le-

gal and ethical aspects of the study, as well as an stan-

dardized explanation of the “think aloud’ approach

and the prototype. At this point the subject had the

chance to ask questions.

6.1.5 Tasks

The tasks were given to the subject in order to test

whether he ﬁnds the needed functionality, whether

understands the visualization, and how much time he

needs. The scenario data was based on a simulation

program of industrial work processes (M

uller et al.,

2014). The scenario was manually analyzed in mat-

ters of different ergonomic assessments and the crit-

ical problems were added to the scenario data. The

following tasks should be processed while using the

visualization:

• How many highly critical problems occur? (every

analysis methods)

• Is there a period of time wherein an increased

number of highly critical problems occur? Which

one?

• When and where do noise problems occur?

• Describe the two problems between seconds 87

and 95!

– How severe are these problems? (your subjec-

tive impression)

– What are their values? (every analysis method)

– If there is any bending in the upper part of the

body: what is the angle of the bending?

– If the workman has an object in his hand: What

is its weight?

– What is the workman doing at this moment?

The relevance of the tasks to the ergonomists work

was conﬁrmed by some experts.

6.1.6 Questionnaire

Afterwards, the participants were confronted with a

questionnaire, which consisted of 14 questions (VBG,

2016) that tested for the aspects of software er-

gonomics as stated in Section 6.1.1. The answering

of the questionnaire took about 10 minutes. The an-

swers were given in German grades (1 - very good, 2

- good, ..., 6 - insufﬁcient).

6.1.7 Analysis

Finally the qualitative data (the observers notes, video

recordings, interview notes and the free comments

from the questionnaire) was coded and categorized.

We did an open coding and used an afﬁnity diagram

(Courage and Baxter, 2005, pp. 715ff) as method for

categorization. Several researchers were involved in

the analysis process in order to ensure objectivity. The

analysis of the questionnaires included the computa-

tion of the arithmetic means, thus giving a tendency

on the fulﬁllment of the ergonomic aspects.

6.2 Results and Discussion

Altogether, every participant was able to solve the

given tasks with the help of the prototype. Hence,

its effectivity was veriﬁed. The time needed for solv-

ing the tasks was between 14 and 39 minutes (without

brieﬁng, questionnaire, and interviews). Each subject

that needed more than twenty minutes for solving the

tasks, did a very detailed description of the prototype.

The study revealed advantages and disadvantages of

the interactive visualization. First we specify the ad-

vantages and disadvantages of the overall picture of

the visualization. Afterwards, we concentrate on sin-

gle elements. The latter advantages and disadvantages

can be categorized in:

• recognizing the functionality of the interactive el-

ements

• perception of time segments

• getting an overview of the situation

• detailed analysis of ergonomic problems

6.2.1 Overall Picture

The overall tool was helpful in solving the tasks at

hand. All possibilities of interaction were detected by

the users. At the same time they considered the han-

dling as complex, especially for inexperienced users.

The selection of single problems was denoted as intu-

itive. The characteristics, that had some inﬂuence are

listed below:

Starting the Tool: Before examining ergonomic

analyses, the data has to be loaded. Most of the

test persons did this very intuitively, but one was

somehow confused. The subject tried to load

the data by pressing the play button of the video

player. Another subject proposed to show a start

Visualizing Ergonomic Data of Industrial Work Processes: A Design Study

279

screen with some hints on the ﬁrst steps, e.g. on

how to load the data.

Help: The help buttons seemed to be hard to see.

Two participants proposed to position help ele-

ments directly at the place that requires it. How-

ever, showing a help as tooltips next to the ele-

ments, may interfere with the work ﬂow, e.g. if

they appear while they are not needed. Thus, we

should realize this direct help conditionally. Then,

the user would be able to switch this functionality

on or off.

Layout: One of the subjects addressed the white

space. He suggested to use it to show additional

information about the problems. This may cause

an even more complex visualization. Further-

more, the test persons experienced the layout as

unbalanced. This appeared especially when less

than ﬁve problems were selected, that caused the

disappearing of the buttons for choosing the next

ﬁve problems and, thus, the timeline was longer

than the line of pictograms. In order to align these

elements the buttons should rather be masked than

disappeared.

Colors: The color coding was well understood by the

test persons. Nevertheless, one subject wanted

to have a different color coding for each assess-

ment method and another one preferred a color

coding from green to yellow to red. We deliber-

ately avoided a color coding that highlights any-

thing else than problematic situations. Other sub-

jects complimented on this fact.

Readability: One subject wanted larger buttons and

larger letters. No other (negative) remarks were

done concerning readability.

Form of Representation: The concept of the infor-

mation levels and its meanings was not obvious

to all of the test persons. For instance, the time-

line was not identiﬁed as well as the assessment

level. Captions for each section, may solve this

problem.

6.2.2 Pictogram Level

The ﬁrst section that should give an overview con-

tains pictograms, that allow for a quick assessment

of a problem and its neighboring problems. Several

test persons used this section for a detailed analysis

of the problems. The pictograms were perceived as

realistic situations. This perception was supported by

the fact that the men shown at the pictograms were

similar to the digital human being shown by the ﬁlm.

Thus, there was no difference in the level of detail

perceived. Most parts of the pictogram were compre-

hensible to the users and they liked that the neighbor-

ing problems are shown. The test persons expected

the chosen problem to be the one in the middle of

the screen. A revision of the interactive visualization

should consider this. As well as the expectation that

problems that are shown in a line are perceived as se-

quential problems in time. The controls (arrows for

jumping back and forwards) of this section were in-

tuitive, but the button for showing the next ﬁve prob-

lems was never used. Thus, it seems to be unneces-

sary.

6.2.3 Assessment Level

The second layer shows the values of the ergonomic

assessment methods. Especially users without any ex-

perience in ergonomics were unable to see the con-

nection between the pictograms and the assessment

table. Following this connection should be more vis-

ible, a grey shadow is not sufﬁcient. There was some

confusion about the plain ﬁelds for the assessment

methods EAWS and climate, they were interpreted as

the absence of problems. The missing of data should

be shown in a different way than the absence of a

problem, for example as a light grey ﬁeld. Is there a

whole assessment method missed, this line should be

erased from the table. Showing the assessment num-

bers color coded as well as alphanumeric seemed to

be unnecessary for a ﬁrst impression. Showing the

exact number after selecting the problem may be suf-

ﬁcient. These numbers should be complemented by

indicating its unit (e.g. decibel (dB) in the case of

noise). In order to make this tool internationally avail-

able, it should be considered to use the units generally

used in the chosen language.

6.2.4 Timeline

The third section shows every problem on a timeline.

Two controllers are used for selecting a certain pe-

riod in time. The subjects liked this solution and un-

derstood its functionality intuitively. Although, the

test persons often used alternative ways of interac-

tion for selecting a period of time. The relationship

of the timeline and the video sequence was not clear

to all test persons. Two subjects expected that the

whole timeline is synchronized with the duration of

the video and they tried to control the timeline with

the cursor of the video player and vice versa. This

situation uncovered the need of indicating the time

spread of the video sequence on the timeline visually.

Another problematic feature was the partition of the

timeline. This partition is accurate to the second: If

the controller is placed within a second, it automati-

IVAPP 2017 - International Conference on Information Visualization Theory and Applications

280

cally jumps to the beginning of the second. This was

confusing to the test persons, especially when they

tried to select the beginning of a problem, but did not

meet it exactly. Thus the controller jumped back to a

point before the problem. It would be conceivable to

allow only the positioning of the controller on exact

seconds or a second-wise visual scale may put things

right.

6.2.5 Detail Level

The last section should allow for a detailed analy-

sis of the selected problem. It consists of the video

player and a detail view. The detail view was not

part of this evaluation. Concerning the video, one

test person used it not only for a detail analysis but

also for gaining a situation overview. Their ﬁrst step

was watching the video. Nonetheless most of the sub-

jects used the video for detail analysis and they liked

that the video sequence showed directly the selected

problem. As noted above the test persons expected a

synchronization between the video and the timeline.

Hence, a parallel run through the problems on the

timeline, should be done while playing the video se-

quence. Furthermore a participant suggested to mark

the problem directly in the video. Sometimes the con-

trols of the video player were confusing. One subject

has problems in leaving the full screen mode and pro-

posed a backwards button. Furthermore the leaving

of the loop (showing the selected problem) back to

the whole video sequence seemed to be difﬁcult (the

users had to stop the video loop and then to restart it).

A possible solution may be the use of two play but-

tons. One starting the selected sequence and another

one starting the whole video. The advantages and dis-

advantages, should be investigated in another test, in

order to avoid to much complexity of the interface.

6.2.6 Tooltips

At some elements of the visualization tooltips were

used in order to give some detailed information. For

example when hovering over a problem on the time-

line, a pop-up shows the exact time span of the prob-

lem. This feature was widely used by the subjects.

They used it for identifying the starting point of a

problem or for ﬁnding out the exact weight or the

exact body angle at the hints next to the pictograms.

However, the majority of test persons discovered this

functionality rather by accident. Therefore, the infor-

mation shown by the tooltips should also be accessi-

ble on an alternative way (e.g. showing the weights

and body angles next to the pictograms permanently.

6.2.7 Complementary Elements

Sometimes the test persons wished for some elements

or functionality, that was not considered yet. One

subject wanted to select a time span on the timeline

directly by typing its starting and ending point. An-

other test person also wanted to show the video se-

quence correlated to the whole time span chosen on

the timeline. Furthermore, the subjects looked for a

possibility to ﬁlter problems. For example they were

interested to see all problems with a bad body pos-

ture. A zoom function for a more detailed analysis in

the video was suggested. Further wishes, like infor-

mation about the composition of the assessments, are

already planned to be shown in the detail level.

6.2.8 Evaluation of the Questionnaire

The arithmetic mean of all question categories is a

2.4 (good), this means that in terms of software er-

gonomics there is not much need of action. Only

the category “individualization” was badly graded by

the test persons (3.5). During the development pro-

cess we focused on the main requirements as stated in

Section 2. For a ﬁnal product the following aspects

should be considered (VBG, 2016):

• Can the user choose the way of interaction?

(Mouse, keyboard, command prompts, touch)

• Is the software adjustable in terms of assistance

(help, hints, list of abbreviations, ...) and display

qualities (color, text size, ...)?

• Is the software adaptable to the users characteris-

tics (language, skills, cultural background,...)?

Some of these points were already criticized by the

test persons during their walk through. For example

considered one subject the texts and buttons as too

small. The font size as well as the size of the controls

should be adaptable. Further improvements may be

achieved through additional help options. Some have

already been discussed in section 6.2.1 (e.g. tooltips

that the user can switch on and off). Likewise, we al-

ready discussed the implementation of language spe-

ciﬁc features in section 6.2.3. Merely the control by

mouse was not criticized yet.

Additional to these questions the group of experts

was asked about the relevance and efﬁciency of the

prototype in practice. The relevance of the prototype

was considered as “good” by the experts. The visu-

alization is a simple and well arranged interface, that

allows for an analysis of the working processes and

for a detailed ergonomic assessment. The efﬁciency

was seen as moderate. The reasons for this laid in the

font size, the controls on the timeline, the complex-

ity of the visualization, the lack of descriptions about

Visualizing Ergonomic Data of Industrial Work Processes: A Design Study

281

the numbers. Nevertheless the test persons labeled the

tool as usable.

7 CONCLUSION

The facts and ﬁgures from business and research

showed that there is a general need for an adequate

visualization of ergonomic data. In a previous paper

(Heft et al., 2015) we discussed the user requirements

and introduced a new design approach. In this work,

we presented the ﬁnal design including an evaluation

of the implemented prototype. The visualization take

the following user’s wishes into account. First and

foremost, the participants expressed the desire for an

easy-to-use application. The second wish was a user-

friendly presentation of the analysis data. The most

important ergonomic problems should be displayed at

a glance and additional information are easily acces-

sible when required.

The ﬁnal prototype was validated in a user study.

A qualitative study with seven persons, including

three ergonomists, was carried out. The test resulted

in the overall score “good”. Therefore, from the soft-

ware ergonomic point of view, it is not compulsively

necessary to improve the program. Nevertheless,

some features have been worked out which could en-

rich the program (in a subsequent version). All partic-

ipants, especially those of the non-experts, were able

to solve the tasks independently and quickly. Thus

the goal of an interactive and intuitive overall presen-

tation of ergonomically critical situations (over any

period of time) was achieved.

REFERENCES

Aigner, W., Miksch, S., Schuman, H., and Tominski, C.

(2011). Visualization of Time-Oriented Data. Human-

Computer Interaction. Springer Verlag, 1st edition.

Courage, C. and Baxter, K. (2005). Understanding your

users : a practical guide to user requirements meth-

ods, tools, and techniques. Morgan Kaufmann Pub-

lishers, San Francisco, CA.

DIN (2010). Prozess zur Gestaltung gebrauchstauglicher

interaktiver Systeme (ISO 9241-210:2010); Deutsche

Fassung EN ISO 9241-210:2010. DIN-Normen:

Deutsches Institut f

ur Normung. Beuth.

Heft, W., Spitzhirn, M., Bullinger, A. C., and Rosenthal,

P. (2015). An Approach for Intuitive Visualization of

Ergonomic Issues. Springer International Publishing,

Cham.

Institut f

ur Mechatronik e.V. (2016). Institut f

mechatronik e.v. - systemdynamik nach maß.

http://docplayer.org/15119271-Institut-fuer-

mechatronik-e-v-systemdynamik-nach-mass.html

- Access date: 07.09.2016.

Legg, P. A., Chung, D. H. S., Parry, M. L., Jones, M. W.,

Long, R., Grifﬁths, I. W., and Chen, M. (2012).

Matchpad: Interactive glyph-based visualization for

real-time sports performance analysis. Comp. Graph.

Forum, 31(3pt4):1255–1264.

McAtamney, L. and Nigel Corlett, E. (1993). Rula: a sur-

vey method for the investigation of work-related upper

limb disorders. Applied ergonomics, 24(2):91–9.

uller, N. H., Truschzinski, M., Fink, V., Schuster, J.,

Dinkelbach, H.

U., Heft, W., Kronfeld, T., Rau, C.,

and Spitzhirn, M. (2014). The smart virtual worker

- digitale menschmodelle f

ur die simulation indus-

trieller arbeitsvorg

ange. Technische Sicherheit 7-

8/2014, Technische Sicherheit(Ausgabe 7-8).

Nielsen, J. (2016). Why you only need to test with

5 users. https://www.nngroup.com/articles/why-

you-only-need-to-test-with-5-users/ - Access date:

12.02.2016.

Plaisant, C., Milash, B., Rose, A., Widoff, S., and Shnei-

derman, B. (1996). Lifelines: Visualizing personal

histories. In Proceedings of the SIGCHI Conference

on Human Factors in Computing Systems, CHI ’96,

pages 221–227, New York, NY, USA. ACM.

Rosenthal, P., Pfeiffer, L., M

uller, N. H., and Ohler, P.

(2013). Visruption: Intuitive and efﬁcient visualiza-

tion of temporal airline disruption data. Computer

Graphics Forum, 32(3pt1):81–90.

Schaub, K., Caragnano, G., Britzke, B., and Bruder, R.

(2013). The european assembly worksheet. Theoreti-

cal Issues in Ergonomics Science, 14(6):616–639.

Silva, S. F. and Catarci, T. (2000). Visualization of linear

time-oriented data: a survey. In Web Information Sys-

tems Engineering, 2000. Proceedings of the First In-

ternational Conference on, volume 1, pages 310–319.

IEEE.

Tominski, C. and Aigner, W. (2015). The timeviz browser

- a visual survey of visualization techniques for time-

oriented data. http://survey.timeviz.net - Access date:

05.08.2016.

VBG (2016). C2web - barrierefreie web-

sites und ergonomische softwaregestaltung.

http://www.c2web.de/ - Access date: 04.03.2016.

Wongsuphasawat, K., G

omez, J. A. G., Plaisant, C.,

Wang, T. D., Taieb-Maimon, M., and Shneiderman,

B. (2011). Lifeﬂow: visualizing an overview of event

sequences (video preview). In Tan, D. S., Amershi, S.,

Begole, B., Kellogg, W. A., and Tungare, M., editors,

CHI Extended Abstracts, pages 507–510. ACM.

Zok, K. (2010). Gesundheitliche Beschwerden und

Belastungen am Arbeitsplatz: Ergebnisse aus

Besch

aftigtenbefragungen. KomPart, Berlin.

IVAPP 2017 - International Conference on Information Visualization Theory and Applications

282