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Development of a 3D-map interface for touristinformation on mobile computers

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As platform for the TG on the iPAQ the PocketPC OS has been chosen due to the available 3D engine Pocket Cortona from Parallelgraphics. Pocket Cortona is able to load and display VRML files, the Internet standard from the Web3D consortium. It offers an interface in the form of ActiveX controls to include the 3D engine as software component within the application. Since the core of this application is implemented in Java, the interface has been wrapped so that the ActiveX controls can be accessed also with Java. The TellMaris Guide on iPAQ is closely connected to the feature database. Apart from frequently visited areas that can be cached, the data will be downloaded from the server as needed. Only the information of the available data and its spatial coverage is stored on the client. Thus the 3D map will dynamically change according to the user position. The user can fly or walk around in the model and/or adjust his position using the coordinates delivered by a GPS receiver, which is connected via Bluetooth to the PDA. The user can switch between 2D and 3D map. The active view is in the foreground whereas the inactive view is still displayed in a small window in the upper right corner. Due to the low hardware performance only a small portion of the whole dataset can be shown at the same time. When the user moves forward, new buildings and terrain tiles appear in the background. The 2D map is used to provide an overview of a larger area, but the scale of this map can also be changed. The orientation can be changed in steps of 90 degrees. The user position can be shown as dot in the SVG map. Selecting targets is done by pull down menus and the user is guided directly to this target without real routing. For several buildings resp. landmarks there are entries in the tourist base. These buildings can be clicked with the pen and contain a link to the database in the form of a URL. If the user clicks on this, the URL is sent to the tourist server, which returns a HTML page for this object. The page is displayed instead of the SVG map.
The TellMarisOnBoard (TOB) application is one of two clients in the TellMaris System. The TOB supports the tourist directly on the boat trip. The application runs on a laptop and provides 3D services for navigation and actual harbour information and weather forecasts. The main features of the application are • 3D terrain viewer; • 2D map viewer; • GPS Navigation; • Tourist info services; • Weather services. The TellMarisOnBoard application consists of two main components: The navigation component and the info search component. (The navigation component contains functionality for navigating in the 3D map and 2D map. The 3D map and the 2D map will respond to the coordinate stream from a GPS. The user can choose to disconnect the GPS and freely navigate in the 3D map. There are two modes of view: "sail view" and "top view". The sail view simulates the user's view from the bridge. The top view gives the user the bird's eye view over the terrain. The 2D map is used for making the orientation easier and for showing the position of the boat. The info search component lets the user search for relevant information like harbour facilities, cultural events and hotels. These features will be visible in the 3D map as abstract objects like a pinhead, or as realistic objects when available. When the user clicks one of these objects, a description of the object will be displayed. The description usually contains links (URL's) for linking to more information about the object. These objects can be toggled on and off like traditional map layers in a GIS. When the user logs on to the TellMaris system for the first time, he or she can fill out a user preference form. In this form the user can select what kind of information he or she finds most relevant. The user preferences will be stored in the TellMaris database. Technology used The TellMarisOnBoard (TOB) is a standalone application programmed i Java (J2SDK 1.4.1) and Java3D. In addition the Java Communication API (version 2.0) is used for communicating with the GPS over the serial port. The TOB communicate with the server using XML/Web Services via HTTP.
An important part of the TellMaris applications is the tourist information. While the applications give the users an interactive and intuitive graphical interface, Tellus supplies the information the user may request. This information includes accommodation, activities, attractions, events, restaurants, shopping, etc. For this information to be valuable for the tourist, it must be of high qualtity (up to date) and of a fairly large quantity. In addition it must be structured in a way that makes it possible for the tourist to search for his or her choices. For example: Conserts this week in Turku or conserts next month in Tonsberg. For these reasons, it is important for the project and for the final products that this information is available and constantly updated. Through over 10 years of experience, Tellus has come to the conclution that it is the destination management organisations (DMO) that is best suited for supplying this information. They are objective, they have the necessary local knowledge and they need to gather this information anyway in order to complete their primary job successfully. However, many of them do not have the tools necessary to be able to collect, update and distribute this information in the quantity, quality and on the format that the TellMaris and other distribution channels can use. The Tellus DMS is such a tool and has been used by the DMOs in the Tellmaris project in order to supply the above-mentioned information. The Tellus DMS is a Client-Server application that is locally installed in the LAN at each destination. The destination updates the information and replicates it into the Tellus central server. From the Tellus central server the data has been accessed to the webpage (www.tellmaris.com) in HTML and to the TOB and TG as XML data. In 2003 Tellus has developed a new interface for the DMS. The interface is now running in a web browser with a new middleware directly into the central database. In order to run the Tellus DMS you just need a web browser. The new Tellus DMS is based on Microsoft.net technology and are using MS-SQL server as database. The interface is programmed in aspx and asp.
The terrain handling is implemented as a client-server application. In the client part (on the user computer), the data are handled as a continuous level of detail elevation model, with superimposed images. In both cases the data are fetched on an as-needed basis, where only the data required for generating the requested image is loaded. As the user moves around in the virtual terrain the models are updated to maintain the resolution needed to give a usable image, and minimise the resource usage for the client. On the client side the terrain is handled as a right-isosceles triangulation. The triangulation uses a regular split pattern for refinement. This simplifies the algorithms and data structures as the positions of points can be used as indexes into a regular data structure for storing the elevations. Each refinement point also has an approximation error value that quantifies the benefit of adding this point to the terrain model. The approximation errors are projected onto the screen space for evaluating the quality of the currently shown terrain model and deciding if the terrain model should be further refined or simplified. In principle any data structure capable of providing a mapping between a position and an elevation/approximation error pair can be used. A large two-dimensional array could be used, but the storage space required for handling an array of up to 232 × 232 cells would be prohibitive. Large areas of the domain would be covered with null values (as they would represent areas where we do not have data of sufficient resolution or where the terrain is flat). To handle this the project has implemented a sparse associative array with clustering of data that are close in both position and resolution level, and with compression of null areas. The terrain textures are stored in a quad tree of images. The images are stored and compressed individually. In a later version an integrated image pyramid can be used, where several image layers are compactly stored in one structure. Several newer image formats like MrSID, JPEG2000 and ECW support this. Initial experiments using JPEG2000 concluded that the format has promise of high compression rates with few visual artefacts, but the available prototype image decoder was too slow compared to more conventional image decoders. The terrain texture tiles are structured as a quad tree in the client. The nodes in the quad tree are also used as the basic rendering unit for terrain elevations. As we are using a right-isosceles triangulation the triangulation and the tile quad tree are easily interconnected so that a subset of the triangulation is completely covered by a texture tile. The triangles in each texture tile are assembled into a triangle strip for efficient rendering. The texture quad tree is refined to a level where the textures projected onto the screen are approximately the size of screen pixels. The terrain textures are stored as a hierarchy of images on a standard http web server. The file structure of the server is used for storing and querying the files. For each texture tile on the client a hierarchical position code can be computed. The position code is transformed into an URL that is used for requesting the file from the server.
The TellMaris Guide is an application for the Nokia 92xx Communicator series, which is a mobile tourist guide application providing the user with: - A real-time, 3-dimensional view of a city model; - A real-time, 2-dimensional view of a city in the form of a map; - Additional (tourist) information. The application has also been ported to Nokia 7650 phone. The features of the application can be used for a multitude of services, possible examples being: - 3-dimensional way-finding in a city, as the person is already at the place, or in advance, in order to prepare a journey; - The provision of additional, up-to-date information, such as restaurant menus, prices, information about specific points of interest, based on the 3D view of the city model; - An overview of the city and orientation help to reach specific places. Since the application resides on a person's mobile device, the user can at any time receive the latest information right into his hand. Technology used Combining new key technologies such as high-resolution colour display and high-speed mobile email, the Nokia 92xx Communicator series is designed to meet the demanding needs of mobile professionals and corporate users. It depicts a wireless device that brings it all together, combining PDA, wireless office, messaging and e-mail, Internet access and mobile phone. The TellMaris guide for Nokia phones is implemented on top of a 3D rendering engine based on the OpenGL. It provides an uncomplicated way of implementing the view and interaction with a 3D-model on a 2D plane. As the memory capacity of a mobile device is rather limited, it is not feasible to store all information in the device. Thus the TellMaris Guide application uses a wireless middleware technology to transfer the required data to the mobile device.
3D city models consists of two results: 1) a sample implementation of a 3D city model of Turku for mobile applications and 2) methods and practices for use in creating further 3D city models for mobile applications. The methods and practices are the mechanisms for working with and adjusting raw spatial data that result in a workable compact 3D city model for mobile applications. They also serve to help estimate the work effort necessary in constructing new models. A key innovation has been the method by which to concentrate only on such features in the model that help in recognizing the surroundings. This method is difficult to automate, but for a modeller, it is relatively easy to learn which features are essential. One of the prime factors in recognisability of features is the trade-off between details in geometry vs. actual appearance. This was proven in the project user tests. The 3D city models built with these methods and practices were usable within multiple applications and on several platforms. The methods and practices are usable, realistic and exploitable either as part of work procedures or as automated mechanisms.
In TellMaris, a modified version of the UDM format is used for the 3D server. It has been extended in order to store more realistic models such as textured buildings and complex hierarchical structures that occur when these models are created by modelling tools such as StudioMax. It is intended to be used as an internal data format within the feature server and includes the most important capabilities of all involved input and output formats. The topmost class is the Feature, which represents real world objects like buildings and other objects. A Feature consists of a geometrical description and visual description of this object and a list of properties, which can store additional attributes like address, name, age etc. as simple name-object pairs. A Feature can either have Geometry or combine several sub-features (children). This way, hierarchical structures can be represented. For example, a building can consist of many parts like roof, walls, garage etc. These parts can be Features by itself. The Shape combines a geometrical primitive (Simplex) and appearance information like a simple diffuse colour or a texture image. The Simplex can be either two- or three-dimensional. For TellMaris the most important primitive is the FaceSet, storing planar polyhedrons. Two-dimensional Polygons are used to derive ground plans of 3D buildings. A important difference between UDM and this model is, that detailed representations are not stored as independent objects connected to more simple query object, but rather this representation is itself stored and can be queried. As database management system (DBMS) the relational Oracle9i has been chosen. The most important classes are mapped to a relational table schema in this database. Most tables are very similar to the corresponding classes. As new element in the Layer table has been introduced which is responsible to distinguish between several datasets. Every time a new dataset is imported into the database one entry in this Layer table is appended with information about the desired name, the overall 2D-extent, the number of features etc. For each Layer separate tables for the other elements are created, the name beginning with the layer name (LN_....). This way, different layers can be accessed separately increasing the query performance. This schema also supports textured objects as well as hierarchical structures.

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