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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 
  
object model is supported at this level. The third layer is user's 
interface ActiveX layer. Some major interface for building 
applications are provided as ActiveX controls. The fourth layer 
is application layer. Five standard application systems are 
provided here. The end user can directly use these systems by 
importing the application data. Experienced users can stay in 
this layer to build their personalized systems other than these 
standard application systems. They can use any programming 
language that capable of calling ActiveX controls and 
COM/DCOM. A lot of examples are provided to help the use to 
customize their own systems based on these example systems. 
  
  
  
  
  
  
  
  
  
  
Fig 1. Component Architecture of GeoStar v4.0 
Fig. 2 is the module architecture of GeoStar v4.0. The five 
standard application systems are 2D GIS GeoStar (note: this is 
the same name of the whole system), Internet GIS GeoSurf, 
image database management system GeolmageDB, DEM 
application system GeoDEM and 3D city GIS CCGIS. 
Customized systems can be B/S Internet GIS, C/S Intranet GIS 
or hybrid system integrating both Internet and Intranet 
applications. 
  
  
  
  
  
Fig 2. Module Architecture of GeoStar v4.0 
3.3 Data Model 
OGC proposed a simple feature specification in which 2D 
geographical objects are modeled in a hierarchical object 
system. However 3D models are not specified in this document. 
As GeoStar deals with 2D vector objects as well as 3D models, 
images and DEM, an extended object model, refer to Fig 3, is 
developed to address all these geographical information. This 
model is compatible with OGC proposed simple feature 
specification. 
  
  
  
  
Fig 3. Data model of GeoStar v4.0 
3.4 Data management 
Data can be stored in any object-relational database system or 
even user-defined file system. The system provides a common 
data controlling components. Some standard interfaces are 
defined and any classes implemented these interfaces can 
access extended data storage system. For data store in Oracle, 
SQL Server and file format of lower version of GeoStar, a 
group of standard COMs are provided and can be directly 
applied. Users can also define their own data storage strategy in 
Oracle, SQL Server and any other RDBMS and file system 
provided that they implements common data access interfaces 
by themselves. This provides a mechanism to extend the system 
on user’s decision. 
3.5 Integrated platform 
GeoStar is an integrated platform. It supports the integration of 
image, vector, DEM and 3D models within a window or a 
system. It supports B/S application, C/S application and 
integrated B/S and C/S applications. The GeoStar server 
implemented OGC WMS, OGC WFS and OGC WCS. It also 
supports GML for geographical data to transfer over the 
Internet. Fig 4 is a snapshot of WMS client with 2 layers of 
geographic data from two different servers that one is GeoStar 
server. 
    
  
Fig 4. WMS client with two overlaid layers from two different 
WMS servers 
4. EXPERIMENTAL STUDIES OF CREATING SDIS IN 
CHINA WITH GEOSTAR AND ORACLE 
Some experimental studies of creating SDIs in China with 
GeoStar and Oracle are conducted, including three levels of 
SDIs in a hierarchical architecture. The lowest level is large- 
scale Digital Shenzhen, the second largest city in Guangdong 
province. The intermediate level is a mid-scale SDI of 
Guangdong Province, a typical province in south China. The 
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