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Virtual Geographic World: the Web-Based 3D Kyong-Ho Kim Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517 Virtual geographic world: the web-based 3D CIS Kyong-Ho Kim, Kiwon Lee, Ho-Geun Lee: & Young- Lyol Ha GIS Lab. Image Processing Dept. Systems Engineering Research Institute, Yusung, Taejon, 305-600, S.Korea Email: {khkim, kilee, hglee,ylha} @seri. re. kr Abstract To design and implement web-based 3D GIS, the strategic linkage of Java and VRML is first regarded: 3D feature format definition in the passion of conventional GIS including aspatial attributes, 3D feature indexing, 3D analytical operations such as selection, buffering, and near, metric operation such as distance measurement and statistical description, and 3D visualization. In 3D feature format definition, the following aspects are considered: aspatial attributes, spatial information for 3D primitives, multimedia data, visualization information for VRML specification. "Lantern operator" is newly introduced in this 3D GIS. Because this system is implemented by Java applet, any client with Java-enable browser including VRML browser plug-in can utilize the new style of 3D GIS function in the virtual space. 1 Introduction The integration of virtual environment and GIS has been initiated]!]. Since the mid 1990s, 3D GIS on World Wide Web(WWW)[2] has been regarded as one of promising alternatives in the GIS field mainly due to cost-effectiveness and wide accessibility. In this newly emerging approach, Virtual Reality Modeling Language(VRML)[3] shows several Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517 344 GIS Technologies and their Environmental Applications linked aspects with 3D GIS under Internet environment^]. Actually, there are several attempts to use VRML for cartographic presentations and modeling[5]; however, it was confined to displaying dynamically pre-formatted VRML files by other authoring tools in a certain VRML browser. Accordingly, they are not, in some extents, satisfied with fundamentals or key components of GIS: manipulation of real-coordinate spatial data, GIS-type file conversion or transformation, and spatial analysis and so forth. Using VRML 2.0 and interfaces with external programs of Java applet, we built a 3D GIS concepts and implemented those ideas in the manner of 3D GIS applications. In this system, engine parts in charge of managing 3D geo-spatial features and performing spatial analysis and visualizations and user interaction parts are written by Java code and VRML, respectively. Multimedia data such as voice information and image is also linked to 3D features in a somewhat application level, and it is partly similar to basic concepts within 3D hypermap[6]. The system, which was proposed and designed in this research, is considered as a prototype of 3D GIS running on WWW. It can build geographic features of 3-dimensional real world, and can simulate 3D spatial analysis. In future, it is expected that Java/VRML- based 3D GIS including conventional 2D GIS functionalities is realized, and then it is one of important GIS research trends. 2 Java-VRML interfaces Using External Authoring Interface(EAI) linking Java applications to the 3D VRML scene, it can be possible to program Java applications which utilize an interactive user interface using VRML[7]. EAI is a kind of Application Programming Interface(API) to allow the Java applet or application to interact with the VRML scene. This interactivity enables Java applet to build and update dynamically the data in VRML. This nature of EAI makes itself to be applied for various field using dynamic visualization^]. We take the EAI as the method for our web-based 3D GIS application for three main reasons. First, with EAI, we can utilize the functionality of VRML browser featured mainly by the navigation functions. A toolkit approach such as Java3D(currently in developing)[9] requires a programmer to understand the structure of any object imported and to have sophisticated graphic design ability. It can also make it extremely tedious to create and control 3D contents. Second, VRML file can be dynamically built and updated via the EAI, based on data received by Java applets, and in turn, the applet's data can also be dynamically Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517 GIS Technologies and their Environmental Applications 345 updated through the VRML interface. Using this property, we can have the web-based 3D GIS engine such as 3D GIS data handling module, and 3D spatial operators built by Java applet communicate with the 3D geo- spatial world built by VRML files. Third, the web-based 3D GIS applet utilizes EAI and VRML can easily be accessed by any platform having only Java-enable web browser with VRML browser plug-in. Supporting for the low-cost and platform-independent client is one of the main features of this system. 3 System design The system is composed of three fundamental modules(Fig. 1): World manager, Spatial analysis manager, and Multimedia manager. Each of these modules interact with VRML files via EAI. World manager creates and modifies the geo-spatial world in VRML browser. It reads the 3D features, DEM and satellite imagery data from database and converts them to VRML file format. During the conversion process, it holds the connection between the data in Java applet and the components(called node) in VRML file. With this connection implemented by EAI, the changes in Java applet can affects the 3D geo-spatial world built in VRML file form. And the event occurred in VRML world can be detected and processed in Java applet side. Spatial analysis manager performs 3D spatial analysis in Java side and visualize the result in VRML world. For example, the buffer operation on pipeline feature is performed on the 3D chain data on Java applet, and its result is visualized through the conversion to cylinder shaped node in VRML file. The result may also be presented in textual(numerical) or graphical form using Java Graphic User Interface(GUI). Multimedia manager handles the image and sound data contained in geographical features. If the feature selected by user has related image and/or sound data, they can be displayed and played using Java GUI. 4 3D feature format We defined three kinds of 3D feature format for each of node, chain, and polygon feature similar to conventional 2D GIS's feature modeling scheme. Each feature format is composed of four sections; aspatial attributes, multimedia-related information, 3D visualization information, Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517 346 GIS Technologies and their Environmental Applications VRML Browser Modify world Sensor events EAI Spatial Analysis Multimedia Manager Manager (Buffer, Near Distance, Lantern) GUI 3D Features, Image data, DEM, Sound data Satellite image Figure 1: Overall system and 3D geographic primitives. 4.1 Aspatial attributes Aspatial attributes for features are defined well in the Feature Attributes Coding Catalog(FACC) of Vector Product Format(VPF)[10]. In FACC, aspatial attributes are coded by integer values for saving the storage space. Integer value, on user request, is decoded and shown as a meaningful strings and can be displayed on a text window. 4.2 Multimedia-related information In addition to the textual information, multimedia information such as image, sound, and animation can give additional information. Images related to 3D features could be taken from the field in advance. Image Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517 GIS Technologies and their Environmental Applications 347 format now available in Java language is GIF and JPEG, and for sound format, the audio file format(*.au) is available currently in Java. 4.3 3D visualization information As we discussed above, 3D geographic world in VRML is basically composed of VRML nodes. So, the 3D features are also to be visualized by some kinds of VRML nodes. Especially, the geometry(box, sphere, cylinder, etc.) and appearance(color, texture, transparency, etc.) of feature are of importance. 4.4 3D geographic primitives We use three geographic primitives; node, chain, and polygon. These primitives are related by reference. Polygon is composed of ring(s). Ring is a circuit of chain(s). Chain is composed of a list of points. Node means an isolated point. These geographic primitive structures are one of common style of other 2D GIS systems. The noticeable difference is that the point has z-coordinate in addition to x- and y-coordinate. So, by just ignoring the z-coordinates, this system can be projected to 2D plane, and all 2D analytical functions including topological operations can be possible. 5 3D spatial operations Some 3D spatial operations are devised and simulated. 3-dimensional buffer operation and near operations are performed on 3D features and visualized. A newly devised operation named "Lantern" operation is simulated on virtual world. Except for the metric operation such as distance measure, the other operations shown in this paper are for GIS- style spatial analysis focused on the visualization. 5.1 3D feature consulting Each 3-dimensional feature visualized in VRML world has sensor detecting the mouse input. Event handler catch the events from sensor and identify the 3D feature on which the event occurred. Then the feature is consulted for attributes, sounds, and images through each output module. Event handler also alter the appearance of selected feature for user notification. Fig. 2 shows the aspatial attributes and multimedia info- Transactions on Information and Communications Technologies vol 18, © 1998 WIT Press, www.witpress.com, ISSN 1743-3517 348 GIS Technologies and their Environmental Applications Attributes of this feature: Class Name : SCHOOL Name :daeduk Feature(Primitive) Type: POL| Existence Category : Oper^f? Construction Year :1979 Figure 2: Aspatial attributes and multimedia information related to a school feature.
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