Full text: The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

1SPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 
and relational database, and an effective R-tree spatial 
index is created automatically. 
From 2D GIS to cybercity, the data management is a critical 
problem. In cybercity, because the reconstructed 3D geometry 
and rendering, the description of surface character ad material 
parameters are the contents of database. If a system is designed 
to handle the fully fledged 3D data base of an entire city, 
including geometry, photo texture and additional information we 
have to be aware of an amount of some hundred Gigabytes of 
data. And we know, that visualization must handle perspective 
projection and oblique viewing points. Based on the successful 
2D database technology of GeoStar, CCGIS improves the 3D 
data handling including spatial index, data selection and clipping 
in perspective space, data subsection process and dynamic 
loading. The hybrid management system of files and relational 
database is the first choice, but the object relational database 
like Oracle8.i is also supported for some special applications. 
Compared with the traditional 2D GIS, cybercity puts forward 
more higher requirements for data organization and 
management such as, 
(1) the integration of data with different types, raster data like 
DEM and DOQ, and vector data like DLG. 
(2) the integrated applications of multiscale models. 
(3) the fast transformation from database to 3D virtual display. 
In order for the purpose of fast visualization of 3D cybercity data, 
we design an effective data structure combined the R-tree 
concept and LOD concept, and use the object oriented method 
to organize these data. For example, in CCGIS the geometric 
surface has the following structure, 
object ID, feature ID, surface type(convex or concave, the 
concave is consisted with TIN ),3D box range, boundary points 
number and 3D coordinates, texture type and mapping 
Surface object is the basic unit of body, the above structure 
benefits the general rendering methods based on OpenGL or 
DirectX. In order to provide more efficient data access or browse 
for a large area or and LOD control, the 3D model data is 
organized according to the classified spatial index based on an 
extended quadtree code stored as cluster related to the feature 
Visualization is very essential for interactive operation, which 
provides the windows and the tools for designing our habitation. 
Under the support of virtual reality technology, with the help of 
the visualization, the cyberspace replaces the traditional abstract 
2D map and the descriptive documentation used to explain, 
analyze and discuss the planning idea and the development of 
city. While the cybercity displays some vivid pictures to users, 
the designer display the designed definite photorealistic texture 
to the people so they can view the designed city, Which displays 
a vivid 3D city model and overcome the difference of culture 
between the specialist and the clients. They are personally on 
the scene when observing the nature, enjoying the scene and 
knowing the entities. Based on the OpenGL graphic rendering 
language, CCGIS provides the dynamic display and interactive 
platform of 3D city model. By using of different detailed data and 
its combination, different visual impacts are available. Such as, 
the natural topographic feature can be expressed by the shading 
DEM surface with coloring elevations. If DLG or DRG is wrapped 
on to the surface, the exquisite spatial distribution could be clear 
at a glance. If the 3D city model with photorealisitc character is 
imported, then the virtual reality could be available. On the other 
hand, such platform also support plenty of special display impact 
like sky, cloud, color lighting, fog and annotation, walkthrough or 
fly over animation, and various scenes also can be disposed 
interactively very conveniently. As shown in Fig. 3, the pilot 
cybercity projects are obviously attractive. 
Figure 3 The pilot districts of CyberCampus and 

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