3D Maps for Boat Tourists

Transcription

1 3D Maps for Boat Tourists Volker Coors a Ove Gjesdal b Jan Rasmus Sulebak b Katri Lakso c a Fraunhofer Institut for Computer Graphics, Germany HfT Stuttgart, University of Applied Sciences, Germany Volker.Coors@igd.fhg.de b SINTEF Institute of Applied Mathematics, Norway {Ove.Gjesdal; c Nokia Research Center (NRC), Finland katri.laakso@nokia.com Abstract This paper presents the results from a study where 3D city maps is used on mobile computers. The aim of this study is to get feedback from the users on how they experience the use of 3D maps as an interface in search for tourist information. To do this an application is developed that use a 3D map for routing and way finding. The application is tested on a group of boat tourists in the harbour of Tønsberg (Norway). The results showed that a rather large group of people found the use of 3D maps valuable both as a navigational tool and as a tool for geographic orientation. In the paper, also some technical issues that enable the transmission of 3D maps in a wireless network and its use on mobile devices, is also discussed. The research is carried out as part of the EU-Project TellMaris (IST ) Keywords: 3D city maps, mobile computers, location-based services, tourist information 1 Introduction An increasing number of service providers within the business of information and communication technology (ICT), are presently developing so-called Location Based Services (LBS). Such services are usually supported by existing GIS technology extended with functionality for interfacing with a wireless environment. Location Based Services provides application developers with a new set of tools to build new software solutions for the mass marked. Among the fastest growing application areas for Location Based Services are within tourism and travelling. The key issue here is to develop software solutions that provide the traveller or tourist with relevant and

2 updated information on mobile computers that is both clearly understandable and readable. 1.1 TellMaris project The objective of TellMaris (IST , is the development of a generic 3D map interface to tourist information on mobile computers. The interface provides a new concept for creating value added information services on mobile computers for the European citizens related to geographical information. In TellMaris it is used for accessing tourist information relevant for boat tourism in the Baltic Sea area. According to Gjesdal (2002) a relative large number of boat tourists has already a Laptop computer or PC on board. What differentiates TellMaris from other projects is the strong emphasise on 3D map models. Other projects focusing on maps and mobile computing still keep on the 2D map metaphor by providing only simple 2D maps as background information for placement and not for spatial query formulation. In TellMaris the 3D map is considered as the main communication interface for location based information retrieval. 1.2 TellMaris architecture This section presents a brief overview of the TellMaris architecture. As reference, the TellMaris architecture use an architecture that follows the OpenLS initiative (OpenLS 2000) as shown in Fig. 1. In TellMaris two different applications are developed. The TellMarisOnboard application running on a laptop computer and the TellMarisGuide application running on a mobile computers or PDA. In this paper only 3D maps in the TellMarisGuide application will be discussed. In the TellMarisGuide application the Location Services concept is used to be conform to upcoming standardisation activities. Web Map Server Web Map Server 3D Location Mobile Location Service Client GPS & Positioning SW/HW XML Route Sercer Internet or Intranet Mobile Terminal Web Map Viewer 3D GSM Geocoder Web Feature Server Coordinat etransfor mation Location Service Client Fig. 1 Reference architecture for TellMaris

3 2 Concept of 3D maps for Location Based Services 2.1 Three-dimensional maps A lot of cartographers and computer scientists have utilised Virtual Reality in a variety of ways to create three-dimensional maps with varying degrees of success. Robinson et al. (1995) defines a map as a visual representation of a spatial relationship in order to communicate environmental information. The primary theme that ties the material together is map effectiveness in thought and communication. The task of the map designer is to enhance the map user s ability to retrieve information. Dykes et al. (1999) point out that representing reality authentically is not a necessary objective of the map though clear and believable representations are usually desirable. The map should rather represent an abstraction of the reality and emphasise on a selected set of features and their spatial relationships of importance for a specific audience. Whilst some map products provide a high fidelity replica of the vista at a location others aim to extract the information pertinent to the use to which the map will be put from the confusion of the surrounding clutter. Indeed a whole array of map products exists ranging from highly abstract, like an interactive three-dimensional Chernoff maps (O Malley 1998), to extremely realistic ones. However, virtual and augmented reality offers a variety of new visualisation and interaction techniques in order to make maps not more real than real (Dykes et al. 1999) but also more useful than before. 2.2 Transfer rate and rendering of 3D map data In recent years, research has focused on resource adaptive rendering (Martin 2000). Currently, small 3D graphic engines available on PDAs (Personal Data Assistants) can render up to triangles. It is expected that the rendering capability will grow very fast in the future as it did on PCs and Laptops in the past. With UMTS, a reasonable amount of bandwidth (384 Kbit/s in urban areas) will be available in a mobile environment. Combined with 3D compression techniques (Coors and Rossignac 2002) it will be possible to transmit 3D maps in a wireless network and use it on a mobile device. However, the high data volume of a 3D map will be critical even in high bandwidth wireless networks. A three-dimensional model with triangles will lead to a 3 MB VRML file. Transmitting this data via UMTS will last about 60 seconds. A standard compression algorithm like GZIP reduces the data volume to 1 MB and transmission time to 20s. Still, 20s is a long time to wait for a normal user. Algorithms that are specialised on 3D meshes achieve a compression rate about 95%. A triangle model can be compressed down to 180 KB and will take less than 4 seconds for transmission. 2.3 Relevance of 3D features in a 3D map Besides rendering and data transmission, one remaining challenge is to decide how to use 3D objects to create a more informative map. The tourist poses a query to get information. So we have an idea of his or her actual interests. Based on this users

4 inquiry, we derive some knowledge of the importance of features in the database. We propose a dominance function that assigns a dominance value to each feature f in the database indicating the relevance of f according to a given query (Coors 2001). In case of routing the starting point and the destination are of special importance. Eyecatching buildings are also helpful as visual landmarks, especially at points where the routing direction is changing, and should be accentuated in the representation. Further on, additional buildings can sometimes deliver a helpful context, but they can also overload the representation, so that the navigation support is ruined. In our work we specify the degree of abstraction of a feature by a dominance value, which reflects the feature ranking in the request. One influence factor of the dominance value is the relevance of a feature concerning a user specific query. A formal description of distance is specified by a distance function between an attribute of the feature and the corresponding query value. However, not only the query dependent relevance factor influences the dominance of a feature. Actually, the dominance is composed by three components, the relevance factor R, the use of a feature as a reference object O while posing a query, and the general use of this feature as a landmark L. 2.4 Example Fig. 2 illustrates the use of dominance values by showing a sequence of 3D routing maps. The sequence represents the route from the railway station to the Fraunhofer Institute of Computer Graphics in Darmstadt. All buildings along that route are derived from the database by a query and are relevance. All other features, which do not match that query, are not relevant. Start and endpoint of the route are reference objects O, and all prominent features like the castle of Darmstadt and conspicuous building along the route are landmarks L. The dominance of each feature is mapped on the transparency value for visualisation purposes. Features with a no dominance are not shown at all. Features with a small dominance value are show in a semi-transparent style and use one grey colour only. Features with high dominance will attract the user s focus by using a textured model.

5 Fig. 2. Sequences of a 3D route visualisation to Fraunhofer IGD Darmstadt. Navigation landmarks are shown in detail while less important building, transparency is used to give a context but not distracting the focus. 3 Methods and procedures 3.1 Evaluation of 3D maps on mobile computers Empirical results were collected during the evaluation of the first prototype of the TellMarisGuide application. TellMarisGuide is a mobile city guide developed for the Nokia Communicator. Its first prototype was evaluated in the August 2002 in Tønsberg, Norway with a group of ten boat tourists. The application showed the presentation of route instructions in connection with a combination of 2D and 3D maps. The main purpose of this the study was to collect some initial feedback from the users about using mobile 3D maps in the city environment. More tests with later prototypes will be conducted next summer. 3.2 Participants There were in total ten users and one pilot user participating in the tests. All users were selected at Tønsberg harbour without strict criteria. Nine of the actual users were males and one was female. All but one of them were Norwegians, one was from

6 Canada. The ages of the actual users varied from 33 to 63 years, half of them being between 50 and 60 years. Average age was 51,6 years. All users had visited Tønsberg before. About one third had been there less than five times before, second third from 10 to 20 times and the last third over 30 times. Despite of this majority of the users had not seen the map of Tønsberg before the tests. All users were also quite experienced with maps. Almost all of them use maps, especially sea charts, often, two people chose the alternative "occasionally". Users thoughts about their map using skills varied from professional to novice, but most of the participants rated themselves as being professional or skillful map users. 3.3 Test procedure Each test session consisted of three parts: introduction, test tasks and interview. In the first part the project and the application were introduced to the user. The user filled out a questionnaire, with some basic data about age, sex, education and their prior knowledge about maps and the area they visited. Then they get a quick introduction to the test procedure and how the test application was running. The test part included six similar tasks. In all of them the user was asked to go from one place to another. In the first four tasks the participants were asked to use the application with the 2D and 3D map. Starting and target locations were marked in the maps, but no GPS was available to keep the user's current position automatically upto-date. In the last two tasks the test users were asked to use a traditional paper map. Each test session ended with an interview, where the user s opinions about the TellMaris Guide application, the 2D and 3D maps, and the test session were asked. The tests were performed with a laptop running a mobile phone emulator. The laptop was an IBM ThinkPad 240 with an Intel Celeron 366 MHz processor, 192 MB RAM memory and 10.4 inch LCD Active Matrix display with 800x600 pixel resolution and 16-bit colours. 4 Results 4.1 General results Users attitudes towards the prototype were in general positive and 75% of them would like to use this kind of service rather than 2D paper maps and guidebooks. The 3D map itself was found to be a good idea, although many experienced map users thought that an electronic 2D map would be sufficient for them. There were two major problems during the tests: The laptop screen was difficult to look at in sunlight and secondly, the users had to navigate in the model by themselves because no positioning system was available. Both of these issues influenced the users satisfaction ratings. Most of the users (80 %) tried to use the 3D model as a navigational aid while all of them used it to recognise buildings. Some users claimed that non-textured buildings were hard to distinguish from each other, but textured buildings, especially one white building

7 were considered easy to recognise (Fig. 4). Some users complained that comparison between the 2D and 3D maps was difficult, because there was no clear correspondence between them. 4.2 User navigation in 3D maps Apart from matching buildings the most common navigation strategy of a user was to follow the direction arrow in the 3D view, and the target location and current location being displayed in the 2D map. The users also had the possibility to choose the viewing height in the 3D view to switch between walking level (pedestrian view, 1.8m altitude) and flying level (bird s-eye-view, 25m altitude). Interestingly, the flying mode was found to be much easier for navigational purposes. 3D maps were found to be slower to use both in initial orientation and route finding compared to 2D maps. We defined the orientation interval to begin at the moment the user was shown the target location and to end when she starts to walk towards it. Then the route finding interval began which lasted until the user reached the target. An average orientation interval lasted 42 seconds when the users used the 3D map, and 10 seconds when the paper map was in use. Route finding interval times also depend on the lengths of the routes, so a proper measurement is needed. Therefore, we rely on the average speed of the user (optimal route length divided by the average time), which was about 1,1 m/s for the 3D map and 1,4 m/s for the paper map. When the users were asked how they would like to improve the application four things were mentioned frequently. According to the users the 3D model should be more detailed and realistic and the target should be highlighted. Street names should be visible and a zoom function should be included in the 2D map. Fig. 3. Evaluating 3D maps: The white house in the middle was found easy to recognise.

8 5 Discussion and Conclusion The purpose of this pilot study was to collect experience on how to improve future prototypes of our navigation system. The small amount of test users and the fact that the choice of participants was not random, suggest that the results of this study cannot be generalised. However, all users performed the same tasks in different order using four times a 3D map and two times a 2D map. Therefore we collected 40 samples for 3D maps and 20 samples for 2D maps, which makes us confident that the results are relevant for our prototype in spite of the small number of participants. It should also be noted that the majority of the users were males and all of them were experienced with 2D paper maps. It has been shown that males and females use different strategies in navigation (Hunt and Waller, 1999). For example, it is possible that females, who are not accustomed to using maps, would have found 3D maps with landmarks more useful. Despite the observation that experienced male users preferred the familiar 2D maps to the new 3D maps the results were promising. Users were able to recognize real world objects from the 3D model and use these landmarks as navigational aids. Many users also said that even though a 3D map would not give them much additional value, it was more fun to use. Another interesting result was that users generally preferred the flying mode to the walking mode. The flying mode gave them a better overview of the surroundings and helped them in building recognition. References Coors, V. (2001). 3D-GIS in Networking Environments, International Workshop on 3D Cadastres, Delft, NL Coors, V. & J. Rossignac (2002) Guess Connectivity: Delphi Encoding in Edgebreaker, Technical Report, Georgia University of Technology Dykes, J. A., Moore, K.E. & D. Fairbairn (1999). From Chernoff to Imhof and Beyond: VRML and Cartography, Fourth Symposium on the Virtual Reality Modeling Language, ACM Press Gjesdal, O. (2002). Market research in the boat tourism segment, ENTER conference Hunt, E., & D. Waller (1999). Orientation and wayfinding: A review. (ONR technical report N ). Arlington, VA: Office of Naval Research. Martin, I.M. (2000). ARTE - An Adaptive Rendering and Transmission Environment for 3D Graphics. Proceedings of ACM Multimedia Conference, Los Angeles, USA, O Malley, J. (1998). Visualising Multivariate Social Data using VRML, Master Thesis, Birkbeck College, London, Robinson, A.H., Morrison, J.L., Muehrcke, P.C., Kimerling, A.J. & S.C. Guptill (1995) Elements of Cartography: Sixth Edition, Wiley