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A <strong>Wearable</strong> <strong>Computer</strong> <strong>System</strong> <strong>with</strong> <strong>Augmented</strong> <strong>Reality</strong> <strong>to</strong> <strong>Support</strong>Terrestrial NavigationBruce Thomas 1 , Vic<strong>to</strong>r Demczuk 2 , Wayne Piekarski 3 , David Hepworth 3 , and Bernard Gunther 1School of <strong>Computer</strong> and 1 Land Operations Division 2 School of Physics and 3Information Science Defence Science and Electronic <strong>System</strong>s EngineeringUniversity of South Australia Technology Organisation University of South AustraliaThe Levels, SA, Australia Salisbury, SA,Australia The Levels, SA, AustraliaBruce.Thomas@UniSA.Edu.AuAbstractTo date augmented realities are typically operatedin only a small dened area, in the order of a largeroom. This paper reports on our investigation in<strong>to</strong> expandingaugmented realities <strong>to</strong> outdoor environments.The project entails providing visual navigation aids <strong>to</strong>users. Awearable computer system <strong>with</strong> a see-throughdisplay, digital compass, and a dierential GPS areused <strong>to</strong> provide visual cues while performing a standardorienteering task. This paper reports the outcomesof a set of trials using an o the shelf wearablecomputer, equipped <strong>with</strong> a cus<strong>to</strong>m built navigationsoftware package, \map-in-the-hat."1 IntroductionA new physical form of a portable computer hasemerged in the form of a wearable computer [2]. Insteadof the computer being hand-held, it is attached<strong>to</strong> the user on a backpack or belt, as illustrated inFigure 1, leaving the hands free when the computeris in use, and also allowing the user <strong>to</strong> view data inthe privacy of a head mounted display (HMD) [7]. Theapplication areas for this form of computer range fromfac<strong>to</strong>ry moni<strong>to</strong>ring, s<strong>to</strong>ck taking, eld data collection,<strong>to</strong> soldiers in the eld.In common <strong>with</strong> other recent research [6], weare investigating the use of a wearable computer<strong>with</strong> augmented realities in an outdoor environment(WCAROE). We have been working <strong>with</strong> the AustralianDefence Science and Technology Organisation(DSTO) and the Australian Army investigating waysof improving the eectiveness of the dismounted combatsoldier, for which navigation is a signicant task.Figure 1: Backpack version of the wearable computerThe application we are investigating is the use of aWCAROE <strong>to</strong> support navigational tasks, or as we like<strong>to</strong> call it, \map-in-the-hat." We are proposing <strong>to</strong> extendthe use of GPS <strong>with</strong> an augmented reality userinterface. A key objective of our work is extendingaugmented reality systems from room size areas <strong>to</strong>outdoor environments [1].2 Related WorkAugment reality has been used for Heads Up Displaysfor aviation, assistance for surgery [8] and maintenancework [4]. This augmented reality work canbe characterised as requiring precise tracking in smalloperating regions.The work presented in this paper breaks from therequirement of precise tracking in small operating


egions. A few researchers are investigating largearea augmented reality. Most notable is the work ofSteven Feiner et.al. <strong>with</strong> Touring Machine project.The Touring Machine allows uses <strong>to</strong> walk around theColumbia campus and access information via a trackedsee-through display and a hand-held display. Thethree main themes of the their work are as follows:1) presenting University contextual information visuallyconnected <strong>to</strong> the physical world, 2) supporting arelatively large area in which the user is able <strong>to</strong> walkaround in, and 3) combining multiple display andinteractiontechnologies. The work presented in this paperextends this concept <strong>to</strong> a new application, terrestrialnavigation.3 Navigation TaskNavigation is the process which guides movementbetween twopoints, and enables the naviga<strong>to</strong>r <strong>to</strong> knowexactly where they are at any given time. Navigationinvolves position nding, direction nding and measuringdistance. Position nding is typically done byreference <strong>to</strong> a map { a scaled plan of a portion of theearth's surface. The direction is usually assessed byuse of a magnetic compass. When planning a route,the distances <strong>to</strong> be travelled between waypoints aredetermined in case position nding is prevented due<strong>to</strong> poor feature visibility. Distance can be measuredby pacing or time calculations.Atypical navigation task is <strong>to</strong> navigate from pointA <strong>to</strong> point B through a set of waypoints W1...Wn.The user starts at position A and initially navigates<strong>to</strong> position W1. Once at waypoint W1, the user thennavigates <strong>to</strong> position W2. This process continues untilthe nal position B is reached.3.1 Problems <strong>with</strong> Traditional NavigationNavigation using the above means can be quite dicultand requires considerable training and concentration.Time and attention spent onnavigation meansless attention is paid <strong>to</strong> the task environment. Thereare many environments where manual navigation isdicult and error prone. The military attempt <strong>to</strong> cope<strong>with</strong> this by sharing the navigation task amongst theteam and by training and practice. A novel use ofVirtual <strong>Reality</strong> is for terrain familiarisation in naturalenvironments [3] where the user can be trained for aparticular set of waypoints.3.2 Global Positioning <strong>System</strong>With GPS, a naviga<strong>to</strong>r applies a similar technique<strong>to</strong> that traditionally used, except for the addition ofaccurate positioning information. The user knows<strong>with</strong>in the accuracy of the GPS their current location,thereby greatly enhancing their ability <strong>to</strong> plot theircurrent position on a map.4 The <strong>Wearable</strong> <strong>Computer</strong> <strong>System</strong>The core of the wearable computer system usedin our experiments is the Phoenix 2 wearable computer[5]. This system has been used in previous experimentsdescribed in [9, 10], involving test on inputdevices for wearable computers.With our current research, the computer systemhas become a lot more complex, <strong>with</strong> extra peripheralsand more batteries, making it impractical <strong>to</strong> mounteverything comfortably on a belt. Therefore, a backpackwas used <strong>to</strong> carry all the needed components, seeFigure 1. The central computer is Phoenix 2 <strong>Wearable</strong><strong>Computer</strong> (<strong>with</strong> a Cyrix 486DX2/66 Processor,32 MB RAM, and a 850 MB 2.5" hard disk drive.)The operating system is Slackware Linux v3.3 runningkernel version 2.0.30. The GPS system is a TrimbleSVeeSix-CM3 GPS Core Module (NMEA-0183 outputand RTCM-104 input), a Aztec RDS3000 DierentialGPS Receiver Module (RTCM-104 output.) The electroniccompass is Precision Navigation TCM2. TheSony PLM-100 dual colour personal LCD moni<strong>to</strong>r isthe see-through device. A VGA <strong>to</strong> NTSC converterboard is needed since the Sony display requires aNTSC signal.4.1 Software OperationThe main purpose of the software is <strong>to</strong> use the outputfrom the hardware devices, such as the GPS andcompass, <strong>to</strong> produce navigation information which isdisplayed <strong>to</strong> the user, as in Figure 2.To use our system, the user must rst enter a lis<strong>to</strong>f waypoints in the form of WGS84 latitude and longitudecoordinate points. Once the waypoints havebeen entered, the user starts the map-in-the-hat program.Keypresses scroll through the current waypointdisplayed on the screen.The compass at the <strong>to</strong>p of the screen in Figure 2shows where the viewer's head is currently pointed,the small triangle underneath <strong>with</strong> the value indicates


shows the number of GPS satellites in contact <strong>with</strong>the receiver.5 TrialsFigure 2: User's screen viewthe exact direction in degrees true 1 . The diamond onthe display represents the waypoint the user is heading<strong>to</strong>wards, and is positioned relative <strong>to</strong> the compassat the <strong>to</strong>p of the screen it is meant <strong>to</strong> approximatewhere the object would be positioned in the physicalworld. However, perspective corrections have not beenimplemented yet and so the diamond will only overlaythe target exactly when the user is looking straight atit. To the right of the diamond is information showingthe name of the waypoint, and its distance and bearing.When the user is <strong>with</strong>in 1000 meters of the nextwaypoint, the size of the diamond cursor increases asthe user approaches the waypoint.To reach the target, the user looks through the displayand attempts <strong>to</strong> walk <strong>to</strong> where the diamond islocated. If the diamond is <strong>to</strong> the left of the displaycentre, then the user rotates their head <strong>to</strong> the left untilthe diamond is centred on the screen. If the direction<strong>to</strong> the next waypoint is outside the eld of view, thediamond cursor is placed on the side of the screen andlled <strong>with</strong> hash marks. The side of the screen the cursoris placed on indicates the direction for the user <strong>to</strong>turn. The display works in a similar way <strong>to</strong> the headup display used on military aircraft, where a box isplaced around the target on the display, and the pilotcan y the plane <strong>to</strong>ward the target by keeping it inthe centre of the glass.The bot<strong>to</strong>m left portion of the display shows thecurrent date and time. Under this information is theuser's position as a WGS84 latitude and longitude coordinate.The bot<strong>to</strong>m right portion of the display1 True North is the direction of the shortest global arc thatintersects <strong>with</strong> the axis of the earth's rotation, and MagneticNorth points in the direction of the horizontal component oftheearth's magnetic eld at its current location, and not actually<strong>to</strong> True North.We performed three eld trials of our navigationsystem <strong>to</strong> test the system in a realistic outdoor setting.The trials tested three dierent conditions: waypointsa large distance apart, a large set of waypoints, andwaypoints in an urban setting. The limitations of theSONY display power consumption forced us <strong>to</strong> limitthe trials <strong>to</strong> no longer than 2.5 hours each.5.1 Trial 1 { Long DistancesThe rst trial was between waypoints a large distanceapart <strong>with</strong> obstacles between them, such asbuildings <strong>to</strong> force us <strong>to</strong> deviate from the prescribedbearing. This trial included waypoints roughly a distanceof 1.7 kilometres maximum from the startingposition. Because the display has a battery life ofonly 2.5 hours, this trial only tested a start, middleand end waypoint.The navigation system provided accurate bearingand distance information <strong>to</strong> all three waypoints. Deviationswhile walking were needed <strong>to</strong> be undertaken<strong>to</strong> avoid construction works, and the navigation systembehaving accordingly. The accuracy obtained was<strong>to</strong> 5 <strong>to</strong> 20 metres. A problem we noted was that sometimesthe GPS signal would completely disappear inopen terrain <strong>with</strong> no discernible features blocking thesignal, but after a moment ortwo the signal was reacquired.5.2 Trial 2 { Large Data SetThe second trail used six waypoints, derived fromsurvey markers and <strong>with</strong>in a kilometre of each other.The rst three waypoints were <strong>with</strong>in a 30 metreradius of each other, <strong>to</strong> test the system's accuracy.Unfortunately, only20 metre accuracy was achieved.These points were under a set of high-tension powerlines,and this may have been the cause of the pooraccuracy, as the dierential GPS signal was carried ona radio signal.On the nal three waypoints, about 400 metersapart, we were able <strong>to</strong> achieve an accuracy of metresfor two of them and 17 metres for the other. Lighttree cover on occasions interfered <strong>with</strong> the GPS signal,and like the previous trial, the signal was lost fora short period of time out in the open <strong>with</strong> no blockingterrain.


5.3 Trial 3 { Urban SettingThis trial was performed <strong>with</strong> given waypoints wehad not seen before. A series of ve waypoints werevisited, all <strong>with</strong>in 200 metres of each other and in acity environ, <strong>to</strong> assess how the GPS would perform inan urban setting. This was not expected <strong>to</strong> be easyfor the GPS.Initially, no GPS signal was procured due <strong>to</strong> thebuildings and trees prevalent in the city, but threesatellites were obtained <strong>with</strong> a DGPS x by standingin an open parking lot. We followed the bearing <strong>to</strong>the rst waypoint, <strong>to</strong> <strong>with</strong>in 5 metres. The next pointwas found <strong>to</strong> <strong>with</strong>in 10 metres accuracy.Waypoint three was much the same as waypointtwo the diamond cursor jumped considerably <strong>with</strong>inthe nal 20 metre radius. Attempts were made <strong>to</strong>reduce the distance <strong>to</strong> the waypoint by not followingthe bearing when closer than 20 metres, but rather bynding the closest distance measurement. The resultwas an accuracy of 5 metres. Journeying <strong>to</strong> waypoint5, the nal test for the day, produced an accuracy of2 metres.6 ConclusionWith our system, we have demonstrated a handsfree navigational aid <strong>to</strong> a person navigating on foot.The use of a wearable computer system <strong>with</strong> a seethroughhead mounted display provided a functionalplatform <strong>to</strong> develop our system. Dierential GPSproved <strong>to</strong> be eective for locating one's position <strong>to</strong>20 metre and better accuracy.The map-in-the-hat application provided useful visualcues for the navigation task. Further work isneeded <strong>to</strong> better understand the form and conten<strong>to</strong>f the presented information <strong>to</strong> optimise visual cues.It is a delicate balance that must be maintained betweenpresenting enough information and obscuringthe user's view of the physical world.Anumber of observations were made. Firstly, thedigital compass is susceptible <strong>to</strong> vibrations while walkingon rough terrain. Secondly, the see-through displayhas a control <strong>to</strong> adjust the back lighting of thescreen (this adjusts how opaque the screen becomes).which turned out <strong>to</strong> be a very useful feature in changinglight conditions. However, excessive sunlight isaproblem, and obscures the SONY display. Thirdly, increasingthe size of the diamond cursor proved <strong>to</strong> be asubtle but eective cue in determining when the user isbecoming closer <strong>to</strong> a waypoint. Finally as <strong>with</strong> mostwearable computer systems, the power managementproved <strong>to</strong> be a major concern of our system.References[1] Ronald T. Azuma. Survey of augmented reality.Presence: Teleopera<strong>to</strong>rs and Virtual Environments,6(4), August 1997. To be published.[2] Len Bass, Chris Kasabach, Richard Martin, DanSiewiorek, Asim Smailagic, and John Stivoric.The design of a wearable computer. In ACM CHI97, pages 139{146, March 1997.[3] R.P. Darken and W.P Banker. Navigating in naturalenvironments: A virtual environment trainingtransfer study. In Proc. of VRAIS '98, pages12{19, 1998.[4] Samory Karez, Vania Conan, and Pascal Bisson.Virtually documented environments. In Proc. ofISWC `97, pages 158{160. IEEE, 1997.[5] Inc. Phoenix Group. Phoenix 2 <strong>Wearable</strong> <strong>Computer</strong>.123 Marcus Blvd., Hauppauge, New York11788, USA. http://ivpgi.com/.[6] S. Feiner, B. MacIntyre, T. Hollerer and A. Webster.A <strong>to</strong>uring machine: Pro<strong>to</strong>typing 3D mobileaugmented reality systems for exploring the urbanenvironment. In Proc. of ISWC `97, pages74{81. IEEE, Oc<strong>to</strong>ber 1997.[7] T. Starner, S. Mann, B. Rhodes, J. Healey, K.B.Russell, J. Levine, and A. Pentland. <strong>Wearable</strong>computing and augmented reality. Technical Report355, M.I.T. Media Lab, November 1995.[8] A. State, M. Livings<strong>to</strong>n, W. Garrett, G. Hirota,M. Whit<strong>to</strong>n, E. Pisano, and H. Fuchs. Technologiesfor augmented reality systems: Realizingultrasound-guided needle biopes. In Proc. SIG-GRAPH `96, pages 439{446, August 1996.[9] B. H. Thomas, S. P. Tyerman, and K. Grimmer.Evaluation of three input mechanisms for wearablecomputers. In Proc. of ISWC `97, pages 2{9.IEEE, 1997.[10] S. Tyerman and B. Thomas. Functionality andusability of novel input devices on a wearablecomputer. In ACSC'98 - The 21st Australasian<strong>Computer</strong> Science Conference, pages 205{216,January 1998.

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