ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS", Bangkok, May 23-25, 2001 
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RESEARCH ON 3D CITY VISUALIZATION BASED ON INTERNET 
Jing CHEN [1] .Qingquan Ll [1] , Jianya GONG 111 , Bisheng YANG 111 
|1) National Lab for Information Engineering in Surveying, 
Mapping and Remote Sensing. Wuhan University 
129 Luoyu Road, Wuhan 430079, P.R.CHINA 
Email: ¡chen@wtusm.edu.cn ,lqq@wtusm.edu.cn ,bsvanq@263.net 
KEY WORDS: 3D-city model, Visualization, R-tree 
ABSTRACT: 
Following the development of the Internet technique and the growing interests in some applications, such as city landscape, real estate 
management, call for three-dimensional GIS data to be handled via Internet. In this paper, we focus our researches on the three- 
dimensional city visualization on Internet. Firstly, presenting the layer-combined (LC) model for city building model and the GRID model 
for city terrain model. Secondly, the client-server architecture is designed to implement query and interaction. In order to speed up the 
operations with the query analysis and fly over the three- dimensional city scene on the client-side, the R-tree organization of objects on 
the server-side is presented. Finally, a system prototype (CWeb3D) for 3D-city model on Internet is developed which includes 3D 
visualization and operation about querying 3D objects and some query analysis. 
1. INTRODUCTION 
In recent years, the development in Internet GIS is very rapid. 
Internet GIS provides users with access interactive, disturbing 
geographical information. But most of Internet GIS software 
only handles two- dimensional (2D) geographical data. It 
cannot deal with the three- dimensional geographical 
information better. Some researchers (Edmund SIDES 
2000,Siyka Zlatanova 1998) have published three-dimensional 
(3D) geographical data on the World Wide Web using Virtual 
Reality Modeling Language (VRML) and Hypertext Markup 
Language (HTML). However this method only views 3D 
geographical data. It is not much better to query and operate 
the 3D objects. Following the development of Internet 
technique and some applications such as city landscape, real 
estate management, The growing interest in 3D city data of 
wide range of local and remote users demands a Internet 3D 
GIS providing extended techniques for data query, visualization 
and interaction with three-dimensional (3D) GIS data via 
Internet, as well as, user-friendly, easy-to-use, standardized 
Graphics User Interface (GUI). 
In order to visualization and interaction with 3D city data via 
Internet, building 3D city model is required. Up to now, so 
many approaches about auto reconstruct and 
semi-reconstruct building city model have been developed. 
For example: CC-GIS (Wang. XH, Gruen, 1998), this system 
includes vector and raster as well as attribute data and uses 
point, line and surface describing a building. Forstner(1999) 
construct building model from image using automatic and 
semiautomatic acquisition method. Due to the complexity of 
buildings, especially the roof of buildings, so many 
researchers pay attention to the data model and structure. A 
serial of data structures are taken into account, for instance: 
CSG, BR, TIN, Grid, TEN, FDS and hybrid structure (Martin 
J, 1992, Pilout M., 1994, R. Li, 1994, Molenaar M, 1992, 
Qingquan Li, 1996). Although these methods are very 
efficient in reconstructing buildings and visualization, most 
of them are used at PC system or workstation system. They 
are not used to construct 3D city model on Internet. The 
paper presented a layer-combined (LC) model for city 
building model. Generally the data structure of GRID model 
(a kind of the DEM model) is sample and the terrain of city is 
plainness, so the GRID model is used to construct the city 
terrain model. 
The following sections are arranged as follow. Firstly, in order 
to view the 3D city data, building the 3D-city model is needed. A 
layer-combined (LC) model for city building model and GRID 
model for city terrain model are presented. Secondly, the 
system architecture for visualization and query, presented here, 
is typical client-server architecture. In order to speed up the 
operations with the query analysis and fly over the three- 
dimensional city scene, use of the R-tree organization of 3D 
objects at the database on the server-side. Finally, an 
application system (CWeb3D) for 3D-city model on Internet is