An Interactive Augmented Reality System for

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Open-air heritage sites have started making use of different types of tourist guides in order to attract a larger ... is the ability to filter information according to the.
Workshop on Virtual Museums, 8th International Symposium on Virtual Reality, Archaeology and Cultural Heritage, VAST (2007)

A Mobile Framework for Tourist Guides F. Liarokapis1, D. Mountain2 1

Coventry University, Cogent Computing Applied Research Centre, Department of Computer Science, Coventry, CV1 5FB, UK 2 City University, giCentre, Department of Information Science, London, EC1V 0HB, UK

Abstract Open-air heritage sites have started making use of different types of tourist guides in order to attract a larger number of visitors as well as educate them in a more challenging manner. However, most of them are still using static audiovisual guides which usually require input from visitors to operate. On the contrary, location-based heritage guides offer a number of advantages over traditional tourist guides ranging from advanced visualisation to intuitive interaction. This paper, presents a novel multimodal mobile framework for tourist guides which can be used in any open-air heritage exhibition. The proposed mobile system allows tourists to switch between three different presentation guides including map, virtual and augmented reality. Localisation of the visitors is established based on position and orientation sensors which are integrated on light-weight handheld devices. To illustrate some of the capabilities of the mobile system two case-studies are presented. Categories: Mobile Guides, Location-based Services, Virtual Reality, Augmented Reality, Interactive Environments.

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Introduction

In museum environments, visitors often use some electronic equipment as sound players, special headsets or personal computers equipped with multimedia applications [SV*04]. On the contrary, open-air heritage sites are expected to have a tremendous growth in the coming years mainly because of the advances in ubiquitous computing [RP*05]. Mobile ubiquitous computing has contributed to the development of an emerging class of services, known as Location Based Services (LBS). The main characteristic of LBS is the provision of information in relation to the spatial location of the receiver [GFD*05]. Modern mobile devices, such as Personal Digital Assistants (PDAs) and mobile phones, present opportunities and constraints when attempting to extend this traditional map-based interface in a digital environment. The major constraint is space: a sign may have a surface area of one square metre or more, however displays on mobile devices are typically less than six by ten cm. This suggests the need to reduce the volume of information still further than for the case of the physical sign. An opportunity in mobile computing is the ability to filter information according to the personal preferences of the device user, to just display

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the particular class of information that they are interested in. Visitors to a National Park may choose to display just information about how industrial uses of the land have affected the area though history, and be presented with a map of all locations in the park associated with industrial development. This is a highly personalised map presenting one type of information at the expense of everything else, essentially placing the device user in the role of map designer, deciding the information that can be included or excluded. An additional opportunity for mobile computing is the opportunity to make the map interface location-aware. Whereas a physical sign presents a single ‘you are here’ arrow, on a mobile device, such a map can update to track the users position to any point on the site, allowing a personalised ‘you are here’ to be generated on demand. This paper presents a novel multimodal mobile framework for tourist and context-aware guides which can be used in a number of open-air heritage exhibitions. The proposed mobile system allows tourists to switch between three different presentation guides including digital map, virtual map and augmented reality assistance in real-time performance. Localisation of the visitors is established automatically in unknown environments based on position and orientation sensors which are integrated on light-weight handheld mobile

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devices such as PDAs. To illustrate the effectiveness of the system two case-studies are presented: one for the national Swiss park and another one for City University. The remainder of this paper is organised as follows. Section 2, presents an overview of relevant work in mobile heritage guides. Section 3, illustrates our novel mobile guide framework. Sections 4 and 5 demonstrate the presentation and tracking technologies used. Section 6, describes two case-studies and section 7 presents our conclusions and future work. 2

Related Work

A survey of mobile guides based on a selection of a set of systems that offer unique features or have been influential in the development of the field has been previously documented [KB03]. The criteria used were derived from some key issues that mobile guides have to face, e. g. the continuously changing situation of the user. However, none of the systems reviewed addressed all the issues but some can already cope with a large subset. Furthermore, a classification of LBS from a stationary versus mobile object perspective as well as algorithms for the efficient support of real applications was researched through the GeoPKDD and NGLBS projects [GFD*05]. For each LBS class, representative examples of potentially useful services are described, focusing on the query processing requirements that arise. A brief overview of the most characteristic context-aware mobile guides that focus on some of the issues involved in navigation was presented in [LBP06] but they cannot deliver a functional system capable of combining all accessible interfaces, consumer devices and web metaphors. The work presented in this paper addresses a fully functional navigational and wayfinding heritage system for unknown urban environments. In terms of heritage applications, one of the earliest guides is Cyberguide [AA*96], which aimed in both indoor and outdoor environments. Localisation for outdoors GPS was used. A major disadvantage of the Cyberguide system is that no client-server architecture was used and all content (maps and other information) were stored on the mobile device thus can work only on a limited area. Another early mobile heritage guide is the GUIDE project [CD*00] developed to provide handheld computer-based tourist guides for the city of Lancaster. Based on client-server architectures and wireless communication protocols the mobile guide approximates its location and then provides guidance and information services through a browser-based interface. Furthermore, the REAL project [BKW02] presents a hybrid navigation system that adapts the presentation of route directions to different output

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devices and modalities. The system assists users to find locations by generating route descriptions. Pocket ArcheoNav [SV*04] a GIS multimedia guide running on PocketPC connected to a Pocket GPS by the Bluetooth interface, developed for some archaeological sites in Sicily. The system has got the main functions of a geographic client to query the database and to change the thematic representation of geographical objects (the features). Moreover, Active Media [RP*05] is a definition of context that has been used to gain access to cultural heritage multimedia contents during a visit to a museum or an archaeological site. The contents are retrieved basing on the context of the visitor; furthermore, the context itself can be used to control the obtained contents. In terms of virtual and augmented mobile exhibitions, the LAMP3D system [BC05] was designed for the location-aware presentation of virtual reality content on mobile devices, applied in tourist mobile guides. Although the system provides tourists with a 3D visualization of the environment they are exploring and synchronized with the physical world through the use of GPS data, there is no orientation information available. An example of an augmented reality guide is the ARCHAEOGUIDE project [GD01] which implemented a powerful mobile system for outdoor augmented reality heritage applications with standard off-the-shelf components. However, the proposed framework was optimized for computing power instead of weight, mobility and robustness. 3

Mobile Framework

The client-server mobile framework uses the capabilities of the LOCUS system [LOC*07] which was developed on top of a mobile platform, known as the Camineo Guide, specifically designed to provide digital guides for tourism [CAM*07]. The Camineo Guide is a user-friendly travelling companion which reveals the richness of an area of interest. Portable and small, it is the same size as a Pocket PC or last generation mobile phone (smartphone). The novelty of the LOCUS system is that it allows users to switch rendering modes between the traditional digital map guide, a virtual reality guide and an augmented reality guide. This allows tourists to select the most appropriate presentation type according to their needs. In addition, the system provides both position and orientation real-time tracking in mobile devices operating anywhere in the word. To our knowledge this is the only multi-modal mobile system designed for PDAs that takes advantage of position and orientation information in real-time. A high-level architectural diagram illustrating the major components of the clientside taking place in the mobile multimodal guide is presented in Figure 1.

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4.1. 2D Map Interface The map interface is perhaps the most obvious and widely used approach in LBS [BG*02], [Gar04], [GS*04], [SF07]. In this work, the digital map interface includes four different representations of maps with different resolutions which can be accessed from the ‘-’ and ‘+’ buttons of the interface. A coloured circle represents the position of the visitor in the map whereas the arrow the orientation. Visitors can interact with the map by selecting one of the eight arrow buttons using the stylus of the device. An example screenshot of our map guide interface is presented in Figure 2.

Figure 1: Multimodal mobile guide framework As the user navigates inside the urban environment, the position and orientation is consciously computed from external hardware devices such as assisted GPS and digital compass and the camera pose is updated respectively. Then depending on the user needs, a map, a virtual reality or the augmented reality interface presents three different navigation options. The mobile guide uses client-server technologies and it specifically designed for PDAs but the description of the architecture is out of the scope of this paper. The main objective of the multimodal heritage system is to provide advanced LBS to mobile users delivered through a web-browser interface (i.e. Pocket Internet Explorer). In terms of functionality, it offers software libraries for integrating positional and orientation information, via Bluetooth, to provide navigational information about the surrounding environment as well as 'mobile search' options based on geo-referenced spatial database. Routing tools are developed to provide advanced navigational assistance to mobile users based upon the experience of previous users, and so may suggest different routes depending on whether the journey is to be taken. 4

Multimodal Mobile Guide Visualisation

There are diverse candidate interfaces for the presentation of spatially referenced information on mobile devices. For location-aware mobile devices, there is the opportunity of presenting spatially referenced information relative to the device user’s current location. Three alternative interfaces have been developed for the presenting information in situ including: •

2D map interface



Virtual reality map interface



Augmented reality map interface

Figure 2: Digital map mobile interface In the pre-digital age, signage at cultural heritage sites often showed maps with ‘you are here’ arrows indicating the location of the sign, and by association, the person viewing it. In addition to the sign’s location and contextual information, the location of specific features of interest was often shown on the map. In order to avoid map clutter, sign designers would often have to work with the site management to decide upon the most pertinent information to display, at the expense of features considered less important. Frequently, these maps displayed a wide range of information from basic utilities (e.g. toilets) to cultural information, such as the location of the most popular site attractions. 4.2. Virtual Reality Map Interface An alternative to the map interface on the mobile device is to use a mobile virtual reality interface, which in

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essence in a realistic 3D representation of the map interface. Details of how the real environment was modelled can be found in [LBP06] and [GLB07]. An example screenshot of the virtual reality mobile guide in operation is illustrated in Figure 3.

the combination of four different types of navigational information including 3D maps, 2D maps, text and spatial sound [LBP06]. However for PDA-based tourist guide applications textual information usually suffices. An example screenshot of textual annotations blended with a live video stream from a mobile device is shown in Figure 4.

Figure 3: Virtual reality mobile interface Both maps and virtual scenes are abstractions of reality. Whilst maps adopt an allocentric (bird’s eye) perspective on a two-dimensional abstraction, virtual reality adopts an egocentric perspective on a threedimensional abstraction. This perspective aims to mirror a visitor’s perspective of a cultural heritage site. For a location-aware system, the viewpoint within the virtual scene can mirror the user’s position with the physical world. The direction of the viewpoint can be set either using heading (taken from GPS) or from a digital compass. The scene itself can be a photorealistic reconstruction of the current sites, or may represent an alternative reality, such as the same scene from a previous time in history [MT05]. This virtual space can be used to present further relevant information to visitors. Labels (such as building names) may be attached to objects in the scene, directions may be presented for a walking tour of a site, or anchor points may allow users to click through to reveal further background information about a feature, for example textual, graphical, audio or video information. 4.3. Augmented Reality Map Interface An augmented reality interface aims to combine real and virtual information within a single view. In the past we have developed a navigational augmented reality interface for Ultra Mobile PC (UMPC) that allows for

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Figure 4: Augmented reality mobile interface On a mobile device, the real information can be provided from a live stream from the device camera. To overlay virtual information in the correct place over the video stream, the location and orientation of the mobile device must be known: this information can be provided from positioning and orientation sensors (GPS and digital compass in this case). This sensor-based approach to registration is not as precise as using visual approaches, such as fiducial markers and natural feature detection [LBP06], but is sufficiently accurate for applying labels to objects in the real world scene. The information displayed can be similar to that described above for virtual reality interfaces: labels, directions and anchor points for further information. However, the major advantage of sensor-based augmented reality is that it can be operation in unknown environments and can work almost everywhere and at anytime. 5

Spatial Localisation

To provide effective location-based services, the continuous tracking of position (x, y and z) and orientation (yaw, pitch and roll) of users in real-time must be achieved. Two different approaches were tested, a sensor-solution and a computer vision approach. The computer vision solution was based on the calculation of features belonging in the realenvironment such as road-signs and parts of buildings

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(i.e. building entrances) [LBP06]. However, computervision provided a very limited range of operation and was not a robust solution for unknown environments. On the contrary, the sensor solution provides sufficient tracking accuracy to unknown environments without the need of calibration prior to the utilisation. The calculation of the user’s position was based on assisted GPS while the orientation on a digital compass. Alternatively, other sensors can be used such as accelerometers and gyroscopes but their main drawback is that their errors tend to sum up over time. In contrast GPS and compass show a constant error, which can be pre-calibrated during the installation of the system [GD01].

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6.1. Swiss Park Guide A location-aware mobile cultural guide was implemented in the Swiss National Park. The Swiss National Park is Switzerland’s only National Park, and is a site of great natural and cultural importance. Visitors are attracted to the dramatic, mountainous scenery (Figure 6), the rare flora and fauna, and the study the history of human influence on the park. In this case study, the map was chosen as the primary interface for the system, and all information stored in the information database was spatially-referenced, allowing it to be placed on a map, relative to the device user’s location.

Figure 5: Tracking hardware including GPS (embedded on the device) and digital compass In the initial prototype, Bluetooth GPS based on the SIRFStar III chipset have been used (i.e. Holux GPSlim 236) due to their small size, long battery life and their massive correlation power, making them especially suitable to for urban environments where signal strength may be limited. However, in the final prototype, PDAs with assisted GPS embedded were used (i.e. HP 6915 PDA and Mio A701). Next, for the integration of a digital compass is not as straight-forward since the hardware is not packaged for consumer use. Specifically, most manufactures provide OEM hardware and software integration needs to be implemented for the specific device. Connecting the digital compass hardware (i.e. Honeywell HMR3300) to a cordless Bluetooth serial adaptor is the solution adopted (Figure 5). A tool has been written to read the data strings from the selected COM port, and these are passed to the tracking component [LRB06]. 6

Case Studies

To illustrate some of the capabilities of the mobile guide two case-studies are presented. The first one was designed for the national Swiss park and an evaluation with 87 participants was performed. The second one was developed for City University and included a qualitative evaluation with six expert users.

Figure 6: Distribution of red deer (darker brown, more likely to find red deer), relative to user’s current location (the red cross) In order to allow visitors to general personalised maps, information was structured according to the activities that visitors participated in (e.g. hiking), frequently asked questions about facilities and access (service / tips), visitors’ main interests (fauna and flora, habitats) and other themes, based upon current exhibitions at the park (basic elements, the course of time, aims 1-2-3, yesterday - tomorrow). By drilling down into these categories and choosing to display the information on a map, the visitors could generate a bespoke map based upon their personal interest and current location, for example, the locations of the sites of lime kilns in the park, the extent of the range of red deer, or places where the flower, edelweiss, is likely to be found. An evaluation study of the system was conducted with 87 participants in the Swiss National Park. Selected visitors were provided with a mobile guide on arrival at the Park information centre, given brief instructions on

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its use, and asked to return in the evening and fill in a questionnaire assessing the usefulness of the mobile guide [KA04]. The main strength of this method was the adaptability of the testing scenario since the mobile guide was used in the field as required, unsupervised without any intervention from the project team. On the contrary, the main flaw was that it could not be guaranteed that all users would utilise all of the system functionality. As a result, the response rate to some of the questions was relatively low. The questions that were presented to the users assessed the performance of alternative geographic filters for mobile information retrieval [MM07]. Overall the user reaction to the guide was very positive. Considering the quality of the information presented by the device, three-quarters of people rated this as either ‘very good’ or ‘good’. Some two-thirds considered the ease of information provision to be ‘very good’ or ‘good’. Crucially, the approach of personalising the information presented to the user by filtering it according to the user’s position appears to have been a valued strategy: over 40% of participants considered this filtered information retrieved to be ‘very relevant’ compared with 12% when the information was unfiltered. As an example, the ‘search around me’ filter was provided the most relevant information with two thirds of the respondents saying that this provided ‘extremely relevant’ results, and over 90% claiming that results were either ‘extremely relevant’ or ‘relevant’. In addition, the ‘search ahead of me’ filter also performs well, (about 89%) claiming that results were either ‘extremely relevant’ or ‘relevant’, and half claiming that the results were ‘extremely relevant’ [MM07]. Finally, presenting information over a map appeared to meet the needs of visitors: 85% of participants found the maps showing information retrieved following personalised searches to be ‘beneficial’ or ‘very beneficial’. 6.2. City University Guide Another customisation that was performed is an extension of the Swiss Park application. Initially the user requirements for navigation and wayfinding were collected based on an expert user evaluation performed at City University. Six expert users from different backgrounds including GIS, geo-visualisation, virtual and augmented reality, information retrieval, humancomputer interaction and psychology were tested [ML07]. Each test took approximately 30 minutes and users were asked to fill in two questionnaires: one about general issues about human navigation and another about testing four hypotheses for virtual navigation. To achieve this, two well known evaluation techniques were applied: think aloud and cognitive walkthrough [DF*04].

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The resulted feedback gave us a very important insight in order to develop the mobile guide for City University. Fist of all, the speed of the navigator affects the navigation process and smooth and slow speed is preferred. All users thought that the field-of-view (FOV) is very important to urban virtual navigation. Having a view of the destination and the route to, is clearly advantage. Also, it is of crucial importance to see visual cues around you when navigating and the eye-level of view is preferred (in contrast to the bird’s eye perspective). However, if the navigation guide allow the navigator to zoom in and out the environment bird’s eye view could be useful in some scenarios. The position of the user is crucial for mobile navigation, as navigation involves knowing your position along a route or destination. In addition, it was found that although the position of navigator is important (especially when making a decision about a route) and changeable, orientation is essential for navigation and it should be considered as one of the fundamental aspects in modern navigation systems. Furthermore, participants mentioned that they mostly use paper maps for navigation and an A-Z map is commonly used when there is a street address enquiry. However, reading paper maps is difficult and the use of digital maps has become very common. It is worth mentioning that all of the participants participated in the study make use digital maps and some of them use them in PDAs as well. As far as the hypothesis testing, expert users reported that the use of textures is an appropriate way for visualization in mobile environments. The use of textures in landmarks is vital but the use of ‘wrong’ textures can be also used in the rest of the 3D map. High realism is also preferred as well as the use of street geometry such as ground, benches, trees, etc. Based on these requirements, a multimodal mobile guide for City University has been designed, that consists of the three domains presented in Figure 1. The application uses position and orientation information at the same time to provide a map view, a virtual reality view and an augmented reality view. The GPS is embedded on the mobile device (i.e. HP 6915 PDA) while the digital compass (Figure 5) is a separate component hidden inside a blue cylinder communicating through Bluetooth technologies. An example of how a pedestrian could use the prototype system in practice in an unknown environment is shown in Figure 7.

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the spatial location and personal interest as well as act as generators of content, adding ‘placemarks’ (also known as spatial bookmarks) that can be shared with other visitors using any of the above visualization domains. Finally, a full evaluation of this case-study is under way with focused groups. 7

Figure 7: Urban mobile guide using GPS and digital compass Using the City University mobile guide, pedestrians can navigate intuitively within the real environment using both position and orientation information on a mobile virtual environment. Additional functionality such as dynamic switching of camera viewpoint from the pedestrian view to a birds-eye view can be accessed from the menu buttons. Another important aspect of the guide is that the digital compass can be also used as a virtual pointer to provide useful information about the surroundings such as ‘what is the name of the building?’ or ‘how far it is located from me?’ etc. An example screenshot of how the virtual pointer is used in practice is illustrated in Figure 8.

Conclusions and Future Work

This paper has presented how mobile interfaces could take advantage of different visualisation and tracking technologies to provide efficient support for tourist guides. In terms of visualisation we are using three domains including the traditional digital maps, virtual 3D maps and augmented reality assistance. We are currently, developing further the interfaces and we plan to perform an evaluation comparing the advantages and disadvantages different presentation domains. Future continuation of this work will focus on achieving better tracking accuracy by integrating differential GPS into the application. In addition, we will develop a hybrid tracking approach by combining the sensor solution with natural feature detection to overcome GPS errors and multipath problems. Moreover, we will extent the textual augmented reality assistance to a richer multimedia experience. Finally, we plan to port the application into commercial mobile phones and other light-weight electronic devices. Acknowledgments Part of the work presented in this paper was conducted within the LOCUS project, funded by EPSRC, through the Location and Timing (KTN) network. The authors would like to thank Prof. Jonathan Raper and Dr. Vesna Brujic-Okretic for their guidance towards the LOCUS project as well as Mr. Christos Gatzidis for creating the virtual reality maps and Mr. Stelios Papakonstantinou for his work in the augmented reality interface. References [AA*96] ABOWD G.D., ATKESON C.G., HONG J., LONG S., KOOPER R., PINKERTON M.: Cyber-guide: A Context-Aware Tour Guide. Wireless Networks 3, 5, (1996), 421-433.

Figure 8: Virtual pointer Currently, we can present this information in textual format but in the future audio descriptions will be added to enhance the experience. This is of particular importance since it allows users to select the information that they want to be presented on the device. Furthermore, visitors can perform advanced searches (i.e. where is the exit?) that take into account

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[GFD 05] GRATSIAS K., FRENTZOS E., DELIS V., THEODORIDIS Y.: Towards a Taxonomy of Location Based Services. W2GIS 2005, Lecture Notes in Computer Science, Vol. 3833, Springer, (2005), 1930. [GLB07] GATZIDIS C., LIAROKAPIS F., BRUJIC-OKRETIC V.: Automatic Modelling, Generation And Visualisation Of Realistic 3D Virtual Cities For Mobile Navigation. In Proc. of the 9th Int’l Conference on Virtual Reality, France, 18-22 (April, 2007), 225-234. [GS*04] GRISWOLD W.G., SHANAHAN P., BROWN S.W., BOYER R., RATTO M., SHAPIRO R.B., TRUONG T.M.: ActiveCampus: Experiments in Community-Oriented Ubiquitous Computing. Computer 37, 10, (2004), 73–81. [KA04] KRUG K., ABDERHALDEN W.: Geographically relevant information for mobile users in protected areas. Report on testing and validation D6.2.1, (October, 2004). [KB03] KRAY C., BAUS J.: A survey of mobile guides. Workshop HCI in mobile guides at Mobile HumanComputer Interaction, Udine, Italy, (2003). [LBP06] LIAROKAPIS F., BRUJIC-OKRETIC V., PAPAKONSTANTINOU S.: Exploring Urban Environments using Virtual and Augmented Reality. Journal of Virtual Reality and Broadcasting, GRAPP

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