Virtual Geographic World: the Web-Based 3D Kyong-Ho Kim

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

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

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 VRMLfile .Th e 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,

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

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-

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. Sound can be heard when the "Sound" button is clicked.

rmation(sound and image) related to a school feature selected by user.

5.2 3D Buffer operation

Buffer operation for 3D geographic features is available for a lot of 3D spatial query and thus, plays important role in decision making process.

3D buffering on point-shaped feature can be applied for the analysis of 3- dimensional pollution area caused by point sources. Analysis process is visualized using Sphere node of VRML. 3D buffering on line-shaped feature can be used when decide position for laying the water-pipe, gas- pipe, electric cable, or telephone cable under ground. Buffering on 3D polygon-shaped feature can be utilized for city-planning and landscape architecture simulation. The visualization for buffering on 3D line-shaped feature and polygon-shaped feature is implemented via Extrusion node of VRML. 3D buffering on under-ground water-pipe feature is shown by

5.3 Near operation

Near operation is to find feature(s) located within an extent from a source feature. For example, a query to find all buildings within 100m area from selected point(or feature) is possible(Fig. 4). Near area and features of query result is visualized by coloring. Attributes of those features can

Figure 3: 3D buffering on water-pipe feature under ground

Figure 4: Near operation on 3D building feature

also be consulted.

5.4 "Lantern" operation

Lantern operation is quite newly introduced in this research; using this operation, 3D geographic and geoscience application is possible, beyond limitation of conventionally static 2D GIS. This operation can be applied

350 GIS Technologies and their Environmental Applications

Figure 5: Lantern analysis performed on a point source under ground

for 3D viewshed analysis, UHF's or VHP's audable range analysis, and decision for optimal position of transmitting tower. When the source position, effective length, effective angle, and the orientation is specified

by user, Lantern operation can be performed(Fig. 5).

6 Conclusions

In this paper, we applied VRML, Java, and EAI technologies to design and implementation of 3D GIS on WWW environment. Although 3D GIS

itself is now research-based stage, not reached commercial market stage yet, this approach can demonstrate some advantages over conventional GISes of 2D GIS, 3D CAD-based data generating system, and even Web

mapping system: cost-effectiveness through utilization of VRML browser, dynamic interaction between VRML and Java, and public accessibility of platform independency and 3D spatial operation functionality. In this

system, 3D feature formats which is comprised of four sections: aspatial attributes, multimedia-related information, 3D-visualization information, and 3D geographic primitives. 3D features are generated by extruding the

ground face and dynamically displayed with DEM and satellite imagery in plug-in VRML browser. As for 3D GIS operator, analytical functions such as 3D buffer and near are implemented. Moreover, "Lantern"

operation is newly devised in this research, and it is expected that wide 3D GIS applications using this operator can be realized in future. Whereas,

GIS Technologies and their Environmental Applications 351

GIS's metric functionality dealt with real geo-coordinate system is included in this system, as normal GIS component. Multimedia data such as text, sound, and images linked to geographical features sometimes play a great role in decision-making[l 1] in end-user level. As further works in this approach, algorithms of computational geometry are necessary for displaying of complex 3D geographical objects facing in our real-world, building of 3D data structure, and devising of 3D GIS operators, and it is still progressing. The technological strategy to handle large data set is also being established. Finally, it is thought that web-based 3D GIS, proposed in this research, can play a significant role in development of new GIS application field and provision of more advanced decision- making methodologies.

References

[1] Neves, N. et al., Cognitive spaces and mataphors: A solution for interacting with spatial data, Computers & Geosciences 23(4), 483- 488, 1997.

[2] Rhyne, T. M., Going virtual with geographic information and scientific visualization. Computers & Geosciences 23(4), 489-491,

1997.

[3] VRML, The Virtual Reality Modeling Language(VRML) 2.0 Specification, http://vrml.sgi.com/moving-worlds/spec/partl, 1996.

[4] Fairbairn, D., The use of vrml for cartographic presentation. Computers & Geosciences 23(4), 475-481, 1997.

[5] Tilmann, R., A world of worlds, http://www.meshmart.org/wow/, 1997.

[6] Kraak, M-J, Driel, R. V., Principles of hypermaps. Computers & Geosciences 23(4), 457-464, 1997.

[7] Marrin, C,, Mccloskey, B., Sandvik, K., Chin, D., Creating Interactive Java Applications with 3D and VRML, Silicon Graphics, Inc.,

http://cosmo.jsgi .com/products/player/developer/eai, 1997.

[8] Kimen, S., The New Dimension of Visual Finance. Transaction

352 GIS Technologies and their Environmental Applications

Information Systems, http://vrml.sgi.com/features/ticker/ticker.html, 1996.

[9] Deering, M. F., Sowizral, H. A., Frequently Asked Questions JavaSD.

Sun Microsystems, Inc., http://java.sun.com/products/java- media/3D/fbrDevelopers/|ava3dfaq.html, 1997.

[10] MIL-STD-2407, Military Standard, Vector Product Format. 1993.

[11] Cartwright, W., New media and their application to the production of map products. Computers & Geosciences 23(4), 447-456, 1997.