Decreasing Physical Burden
using the Following Effect anda Superimposed Navigation System
Yuji Makimura, Hiroki Yoshimura, Masashi Nishiyama, and Yoshio Iwai
Graduate School of Engineering, Tottori University
101 Minami 4-chome, Koyama-cho, Tottori, 680-8550 Japan

Abstract. We propose a novel navigation system using a virtual guide
who walks in front of the user and induces the following effect. Whenusing existing navigation systems, the user has a high physical burden
because the user continuously moves their gaze and head to look at the
map and landmarks on their journey. Employing our system, the user
simply follows a virtual guide superimposed on the real world. There isno need for the user to look at the map and landmarks while walking. In
experiments, we measured changes in the gaze direction and head pose
while the user walked with a real or virtual guide. We observed thatthe guides provided the following effect to the users and alleviated their
physical burden.

1

Introduction

There is a demand for navigation systems that intuitively support users while
walking. Conventional navigation systems such as Google maps [4] support theuser using the steps illustrated in Figure 1. Before the user walks, he or she
sets a destination (S1) and selects a route suggested by the system (S2). While
walking, the user checks their current position on the map (S3), and searches forlandmarks in the real world (S4). If the user understands their current positionin the real world, he or she can determine their travel direction (S5). Otherwise,
the user laboriously repeats S3 and S4 until he or she correctly understands
their current position. While repeating these steps, a user frequently moves theirgaze and head to see the system and landmarks, as illustrated in Figure 2. Auser can feel a physical burden from these movements. In particular, existing
methods [6, 13, 8] using global navigation satellite systems and digital maps on
mobile terminals produce a physical burden because they require the user torepeat these movements.
In this paper, we tackle the challenging problem of decreasing the physicalburden by reducing gaze and head movements using a novel navigation system.
To reduce these movements, we must intuitively indicate the direction of travelto the user. Existing methods [2, 10] use simplified maps or simple messages
to enhance the navigation system. However, these methods sometimes do notII
Before walking

While walking

S1. Set destination
Map

S3. Check current position on map

S4. Search landmarks in real world
S2. Select route
C1. Understand current
position in real worldNo

Yes
S5. Determine travel direction

Fig. 1. Overview of a navigation system.
Gaze
Head

Fig. 2. Searching landmarks.

reduce head and gaze movements because the user must read the simplified
maps or simple messages.
Here, we consider a situation where a guide suggests the travel direction byalways walking in front of the user. In this situation, we believe that the gaze andhead movements are reduced because the user simply follows the guide. Whenthe attendees of a conference go to a banquet venue, for example, following a
guide is the easiest way to smoothly reach the venue. We call this the following
effect. This effect is known in the field of car navigation systems [9] and indoor
navigation systems [14]. We show that the virtual guide provides the following
effect when the user walks in an outdoor environment.
In this paper, we show that the following effect experimentally decreases
the physical burden, by measuring the gaze and head movements of a walking
user. Furthermore, we developed a navigation system that uses a virtual guidesuperimposed on the real world through a head-mounted display (HMD) andevaluated the reduction in movement. The rest of the paper is organized asfollows. Section 2 shows that the physical burden of the user is reduced by
the following effect when the user walks with a real guide. Section 3 shows theevaluation of a virtual guide with an HMD. Our concluding remarks are given
in Section 4.

III

N1 : Real guideN2: Signpost

N4 : Combination

N3 : Mobile terminal

N5 : Map

Fig. 3. Navigation methods that were compared to evaluate the following effect.

2

Following effect cased by a real guide

2.1

Comparison of conventional navigation methods

To observe the following effect, we measured the movements of head poses andgaze directions while walking. We compared five navigation methods as illustrated in Figure 3.
N1 : (Real guide) The user followed a real guide who was always walking infront of the user.
N2 : (Signpost) The user saw signposts set at junctions.
N3 : (Mobile terminal) The user could check their current position on amobile terminal at any time while walking.
N4 : (Combination) The user used a combination of N2 and N3.
N5 : (Map) The user carried only a real map printed on paper.

2.2

Evaluation protocol of the real guide

In N1, a real guide, who fully understood the route and the map, walked about
2 meters in front of the user. The real guide showed the travel direction atjunctions by bending forward without talking to the user. The real guide walked
at a constant speed and checked that the user was following behind at intervalsof 30 seconds. In N2, signposts at junctions showed the travel direction using
arrows. The user was able to see the signposts at a distance. In N3, the user
carried a mobile terminal (SONY XPERIA mini) and could check their current
position using a map application at any time during their journey. In N4, the

IV
D

D
S

S

S

D

S
D
S

D

Fig. 4. Maps and routes used in the experiments (S denotes the start, D the destination,and the heavy line the route).

user saw the signposts of N2 at junctions and carried the mobile terminal of N3.
In N5, the user carried the printed map that dictated the route and destination.
The user could look at the printed map at any time during their journey. Notethat we provided the map to the user in all conditions from N1 to N5. We
conducted the study for four participants (average age ± standard deviation of
22.0 ± 1.2, two male, two female) as the users. We prepared five routes (eachwith length of 600 m and having six junctions), as illustrated in Figure 4. We
randomly set the route and the destination for each user in our evaluation.
To measure the gaze direction while walking, we used the wearable device(Takei TalkEye Lite) shown in Figure 5(i). The sampling rate of the device was
30 Hz. To measure the head pose while walking, we used the wearable device(MicroStrain 3DM-GX-25) shown in Figure 5(ii). This device can measure theacceleration, gyroscope , and magnetic field. The sampling rate of the device was
100 Hz. The gaze direction is given on x and y axes of Figure 6 (i). The headpose is represented by the roll, pitch, and yaw axes of Figure 6 (ii). The origin of
the axes corresponds to the state that the user stands upright and looks straightahead. We measured the relative angle from the origin.
2.3

Evaluation with a real guide

Changes in gaze direction Figure 7 shows the distributions of gaze movements while walking. The gray level corresponds to the frequency of the gaze inthat direction, and (X, Y ) = (0, 0) represents that the user was looking straightahead. We normalized the number of samples of gaze directions for each user because each user walked at a different speed. We see that the frequencies aroundthe center direction in N1–N5 are higher than those for other directions. We

V(i) Gaze(ii) Head pose

Fig. 5. Equipment for measuring the gaze direction and head pose.
Y
Yaw

0

X
Roll

(i) GazePitch(ii) Head pose

Fig. 6. Rotation axes for representing the gaze direction and head pose.

believe that this phenomenon is due to the effect of the center bias [15]. Furthermore, we see that the real guide (N1) reduced the movements; i.e., the user
looked straight ahead more for N1 than for N2–N5.
Table 1 gives that the averages and standard deviations of gaze directions
computed from absolute values of angles. We see that the averages of N1 aresmaller than those of N2–N5, and the standard deviation for the Y directionof N1 is smaller than those of N2–N5. We believe that the gaze direction is
attracted to the center by the virtual guide.
Changes in head pose Figure 8 shows the distribution of head movement
while walking. We normalized the number of samples of head poses for eachuser because each user walked at a different speed. We unified the sum of the
distribution for each method. We used the pitch axis to indicate the change
in upward and downward movement of the head. The head faces the front for
R = 0, downward for R > 0, and upward for R < 0. We see that the real guide
Table 1. Averages and standard deviations of absolute gaze directions [degrees].

X
Y

N1
10.4±9.5
8.2±9.4N211.0±9.6
9.4±10.9N311.5±9.6
12.6±12.6N411.0±9.6
10.2±11.0N512.6±10.4
10.9±11.4

VI
40

Y[deg]

20
0
-20
-40
-40 -200
20 40
X[deg]
N1 : Real guide-40 -200
20
X[deg]
N2: Signpost

40-40 -200
20 40
X[deg]
N3 : Mobile terminal

0
20 40
X[deg]
N4 : Combination-40 -2040

40

Y[deg]

20
0
-20
-40
-40 -20

0

0.01

0.02

0.03

0.04

0
20
X[deg]
N5 : Map

0.05

0.06

0.07

Fig. 7. Distribution of gaze while walking using different navigation methods.

(N1) reduced the head movement; i.e., frequencies around 0 degrees were higher
than those of other angles. We believe that the real guide reduces the verticalmovement of the head of the user looking at the map.
Table 2 gives the averages and standard deviations of head poses computedfrom the absolute angle of the pitch axis. We see that the average and standard
deviation of N1 are lower than those of N2–N5. A previous report [5] describedthat the burden of the neck vertebrae increases to 2.3 kg when the head moves
downward from 5 degrees to 10 degrees. We believe that the head pose is attracted to the center by the virtual guide. Note that the average values for the

Table 2. Average and standard deviation of the pitch axis of the absolute head pose[degrese].
N1
5.1±5.1

N2
6.1±7.5N310.1±11.1

N4
7.8±9.8N5
8.7±9.8

VII
0.12

Frequency

0.1
0.08
0.06
0.04
0.02
0

-40

-20

0
20
R[deg]
N1 : Real guide

40

-40

-20

0
20
R[deg]
N2 : Signpost

40

-40

-20

0
20 40
R[deg]
N3 : Mobile terminal

0.12

Frequency

0.1
0.08
0.06
0.04
0.02
0

-40

-20

0
20 40
R[deg]
N4 : Combination

-40

-20

0
20
R[deg]
N5 : Map

40

Fig. 8. Distributions of the head pitch for the different navigation methods.

angle about the yaw axis in N1–N5 were almost the same. The users sometimes
moved their head horizontally to navigate obstacles when walking. The averagesof the angle about the roll axis were zero in N1–N5. The users did not tilt theirhead when walking.

3

Navigation system using a virtual guide

3.1

Design of our navigation system

Head and gaze movements were reduced when using a real guide as describedin the previous section, and we thus believe that the following effect decreases
the physical burden. We therefore designed a novel navigation system that uses
a virtual guide superimposed on the real world. Our system displays a virtual
guide to the users on an HMD, as illustrated in Figure 9. We compared oursystem with four navigation systems in terms of effectiveness, as illustrated in
Figure 10.
V1 : (Virtual guide) A virtual guide walked in front of the user to indicate
the travel direction.

VIII
Real world

Superimposing

Guide layer
HMD
Guide position

Head pose
Control PC

Fig. 9. Overview of our navigation system using the virtual guide.

V2 : (Arrow) A virtual arrow appeared at junctions to indicate the travel
direction.
V3 : (Current position) A virtual map was provided with the current position always shown.
V4 : (Combination) The user used a combination of V2 and V3.
We provided the users with a printed map containing the destination and routefor all conditions. The above systems are alternatives of N1–N4 described in
Section 3.1. Virtual guides are often used in augmented reality applications [12,1, 11], and virtual arrows have been used in a map application [7]. We investigate
whether a virtual guide reduces the physical burden of users while walking in an
outdoor environment.
3.2

Evaluation protocol of the virtual guideTo evaluate the navigation systems, our system controlled the guide or the arrowusing the Wizard of Oz technique [3]. We used an optical see-through HMD(EPSON MOVERIO BT-200). In stably overlaying the guide or the arrow on
the real world while the user walked, we used an operator to control the display
position of the guide as illustrated in Figure 11. We acquired the head pose of theuser using the acceleration and gyro sensors built into the HMD. After showing
the guide or arrow adjusted to the head pose, the operator modified the positions
when there was an error. The operator followed 2 meters behind the user, andmodified the display position by monitoring a live video sequence obtained froma camera built into the HMD . In V1, we adjusted the parameters of the virtual
guide such that the virtual guide was 170 cm in height and displayed about 5 m
in front of the user. In V2, we displayed an arrow 5 m before reaching a junction.
In V3, we showed a map and the current position such that the visibility of theuser was not disturbed.

IX

V1 : Virtual guideV2 : Arrow

V3 : Current position

V4 : Combination

Fig. 10. Navigation systems for evaluating the following effect.

HMD

User
Operator

Control PC

Fig. 11. Operator and user with equipment for evaluation.

Twelve participants (average age ± standard deviation of 21.5 ± 0.4, 10
males, two females) acted as the user. We used the same routes described in
Section 2.2, and randomly set the route and destination. We used the same sensor
described in Section 2.2 to measure the head pose of the user. Note that we did
not acquire the gaze direction of the user because the gaze sensor disturbed the
HMD.
3.3

Measurement of the head pose with the virtual guide

Figure 12 shows the distribution of the head movement around the pitch axis
while walking using navigation systems V1–V4. We used the same axes andevaluation protocols described in Section 2.3. We see that the peaks of the histograms for V1 increased near the frontal direction. We believe that the virtual

X
0.12

Frequency

0.1
0.08
0.06
0.04
0.02
0

-40 -200
20 40
R[deg]
V1 : Virtual guide-40 -200
20R[deg]
V2 : Arrow-40 -20-40 -2040

0.12Frequency

0.1
0.08
0.06
0.04
0.02
0

0
20 40
R[deg]
V3 : Current position

0
20 40
R[deg]
V4 : Combination

Fig. 12. Distributions of the head pitch while walking using the four navigation methods.

guide reduced the head movements of the users. We also see that the head faced
downward more frequently for V2–V4 than for V1. We believe that the users
more frequently checked the printed map during their journey for V2–V4 thanfor V1. Note that the angle about the yaw axis was concentrated around 0 degrees, and there was no apparent difference in the angle around the roll axis.
Table 3 gives the averages and standard deviations of absolute angles of headposes around the pitch axis. The table confirms that the average and standard
deviation were lower for V1 than for V2–V4, and changes in the vertical direction
were small for V1. We observed that the virtual guide superimposed on the realworld reduced the head movement of users while walking.

Table 3. Averages and standard deviations of absolute head poses [degrees].
V1
5.2±5.7V2
7.9±10.1V3
9.2±9.8

V4
7.1±8.4

XI

4Conclusion

We revealed that the following effect induced by a real guide decreased thephysical burden of a walking user, by measuring the gaze and head movements ofusers. We also developed a navigation system using a virtual guide and evaluatedthe reduction in head movement.
As part of our future work, we will expand our analysis to long-term experiments on the proposed navigation system and develop a method that assists
users to avoid hazards.

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