A Wearable Augmented Reality System for Navigation
Using Positioning Infrastructures and a Pedometer
Ryuhei TENMOKU Masayuki KANBARA Naokazu YOKOYANara Institute of Science and Technology
8916-5 Takayama, Ikoma, Nara, 630-0101 Japan{ryuhei-t, kanbara, yokoya}@is.aist-nara.ac.jp
Abstract
This paper describes a wearable annotation overlay system using augmented reality (AR) techniques. To realize
AR systems, the position and orientation of user’s viewpoint should be obtained in real time. The proposed systemmeasures the orientation of user’s viewpoint by an inertial
sensor and the user’s position using positioning infrastructures in environments and a pedometer. The system specifies the user’s position using the position ID received from
RFID tags or IrDA markers which are the components ofpositioning infrastructures. When the user goes away fromthem, the user’s position is alternatively estimated by usinga pedometer.

1. Introduction
Since computers have made remarkable progress in resent years, a wearable computer can be realized[1]. At thesame time, Augmented Reality (AR) which merges the realand virtual worlds has received a great deal of attention as anew method for displaying information[2]. If we constructan annotation overlay system for real scene using AR techniques with a wearable computer, it can be applied for manyapplications[3].
To realize wearable AR systems, the position and orientation of user’s viewpoint are needed for acquiring the relationship between the real and virtual coordinate systems.
Usually, Global Positioning System (GPS) is used outdoors,a magnetic sensor is used indoors to measure the user’s position, respectively. Since each sensor can not be used bothindoors and outdoors, if we construct a wearable AR system which can be used indoors and outdoors, we must combine positioning methods for outdoor and indoor environments. However, there remain some problems such that thehardware configuration of the system is complicated and thesystem needs to switch the sensors between indoors and outdoors. Therefore, we propose a wearable AR system which
overlays annotations on real scene images to guide the user
indoors and outdoors seamlessly.

2. Annotation Overlay System on a Wearable
ComputerAR systems which overlay annotations on the real scene
need three kind of information: a position and an orientation of the user’s viewpoint, and an annotation database ofinformation associated with the real world. The system obtains the orientation of the user’s viewpoint using an inertial
sensor which is attached to the user’s headset. The annotation database is stored in a wearable computer.
The proposed system measures the user’s position indoors and outdoors using positioning infrastructures and apedometer. The system identifies the user’s accurate position using positioning infrastructures when the user is near
the components of positioning infrastructures. In this paper, RFID tags and IrDA markers are used as componentsof positioning infrastructures. Both of them record position
IDs, and the proposed system can specify the user’s position
by receiving position IDs with sensors which are equippedby the user. When the user goes away from components ofpositioning infrastructures, the user’s position is estimatedby using a pedometer. The pedometer consists of an electronic compass and acceleration sensors. The former candetect which direction the user walks toward. The lattercan count how many steps the user walks. These two data
and the user’s pace make it possible to estimate the user’s
position in the neighborhood of components of positioning
infrastructures.

3. Hardware Configuration of Prototype System
Figure 1 shows a hardware configuration and data flowof the proposed wearable AR navigation system. The user
equips five sensors, a notebook PC and a display device.
Five sensors can obtain the position and orientation of theuser’s viewpoint and the real scene image. These data aresent to the notebook PC. The notebook PC generates annotation overlay images from these data and a database ofannotations which is stored in the PC. The user can see annotation overlay images through the display device which isInertial Sensor
Display Device
INTERTRAX2(INTERSENSE)

User’s Orientation
CameraDragonfly(PointGreyResearch)

Clip On Display(Micro Optical)

(a)

(b)

(c)

(d)

Annotation
Overlay Image

Real Scene Image
RFID Tag Reader

V720 (OMRON)

IrDA Receiver
Pedometer

Figure 2. Annotation overlay images.
Computer

Original
3D Motion Sensor(NEC TOKIN)

User’s Position

Annotation
Database
INSPIRON 8100(DELL)

Figure 1. Hardware configuration of the proposed system.
attached to the user’s headset. Components of the proposedsystem are described in more detail in the following.
Sensors The user equips the following five sensors. The
data obtained with them is transmitted to the computer
through USB, IEEE1394, or serial connection.
Inertial sensor (Intersense: InterTrax2 ) An inertial
sensor is attached to the user’s glasses and measures
the orientation of the user’s viewpoint.
Camera (Point Grey Research: Dragonfly) A camera
is attached to the user’s headset and captures the realscene image from the user’s viewpoint. It can capture
RGB 24bit color image of 640 × 480 pixels.
IrDA receiver (Original) An IrDA receiver is attachedto the user’s bag as shown in Figure 1. The IrDA receiver receives infrared ray including position IDs.
RFID tag reader (OMRON: V720) An RFID tag
reader is attached to the user’s wrist as shown in Figure
1. The RFID tag reader reads the position IDs recordedin RFID tags.
Pedometer (NEC TOKIN: 3D motion sensor) A pedometer can measure pitch, roll, and yaw. It can alsomeasure accelerations in the horizontal directions.
Computer (DELL: Inspiron8100, PentiumIII 1.2GHz,512Mbytes memory) A computer is carried in theuser’s shoulder bag. It holds a database of annotation
information for generating annotation overlay images.

Display device (MicroOptical: Clip On Display) A display
device is a video see-through display device. It is attached to headset as shown in Figure 1. It can present
a 640 × 480 color image to the user.

4. Experiment and Concludion
We have carried out an experiment using the proposed
wearable AR system in our campus. Figure 2 (a) and (c)show the annotation overlay images when the system identifies the user’s position using positioning infrastructures,and (b) and (d) in Figure 2 are ones at the user’s position estimated with the pedometer when the user walks some steps
from components of positioning infrastructures.
We have proposed the annotation overlay system on awearable computer using positioning infrastructures and apedometer. We have also shown that the proposed system
can be used both indoors and outdoors seamlessly throughthe experiment.
Acknowledgments
This research is partially supported by Core Research for Evolutional Science and Technology (CREST) Program “Advanced Media Technology for Everyday Living” of Japan Science and Technology Corporation (JST) and also by the Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports,
Science and Technology (MEXT).

References[1] S. Mann: “Wearable Computing: A First Step Toward Personal Imaging, ” IEEE Computer, Vol. 30, No. 2, pp. 25-32,
2002.
[2] R. Azuma: “A Survey of Augmented Reality, ” Presence,Vol. 6, No. 4, pp. 355-385, 1997.
[3] R. Tenmoku, M. Kanbara, and N. Yokoya: “A wearable augmented reality system using an IrDA device and a passometer, ” Proc. SPIE, Vol. 5006, pp. 478-486, 2003.