The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
5. CONCLUSIONS 
In the geographic visualization visual fidelity and system 
efficiency are always in a dilemma. In the situation which our 
computer resource is limited what we should research is how to 
balance the visual fidelity and system efficiency. 
This paper makes some probing research on this problem. And 
some of the key techniques in the global terrain visualization 
are introduced. For example, the simplified global terrain data 
partition and organizing method, and the improved SPHIT 
wavelet compression method considering the terrain surface 
complexity. 
In the following work more deep research should be done 
on more available methods to calculate terrain surface 
complexity and better evaluation of visualization demand. 
ACKNOWLEDGEMENTS 
This research is partially supported by the Key Knowledge 
Innovative Sub-Project of Chinese Academy of Sciences 
(Kzcx2-yw-126-01), National High-tech R&D Program (863 
Program) (2006AA12Z204), and National Basic Research 
Program of China, 973 Program, No. 2007CB714402. 
REFERENCES 
BEN Jin, ZHANG Yong-sheng, TONG Xiao-chong. TerraVisi 
on: Technical Analysis and its Application in Building Global 
Massive Spatial Data Management System. Bulletin of Survey 
ing and Mapping. 2005,6. 
CHEN Renxi, ZHAO Zhongming, WANG Yinxing. DEM Data 
Compression Based on Integer Wavelet Transformation. Geom 
atics and Information Science of Wuhan University. 2006,4. 
GORE. The Digital Earth: Understanding our planet in the 21st 
Century [EB/OL]. 
Keyhole Inc.,” EarthViewer”, http://www.earthviewer.com/, 
2001. 
Koller D, Lindstrom P, Ribarsky W,et al. Virtual GIS: A Real- 
Time 3D Geographic Information System. Report GIT-GVU- 
96-02, Proceedings Visualization ’95, USA, 1995, 94-100. 
LUO Yong, CHENG Ll-Zhi, CHEN Bo, WU Yi. The Research 
on Digital Elevation Mode Data Compression Arithmetic via 
Wavelets. JOURNAL OF NATIONAL UNIVERSITY OF DE 
FENSE TECHNOLOGY. 2005,2. 
ZHANG Liqiang, ZHANG Yan, YANG Chongjun, et 
al.Effective solutions to a global 3D visual system in 
networking environments. Science in China Ser. D Earth 
Sciences 2005 Vol.48 No.l 1 2032 2039. 
ZHAO Xue-sheng, SUN Wen-bin ,CHEN Jun. Distortion 
Distribution and Convergent Analysis of the Global Discrete 
Grid Based on QTM. Journal of China University of Mining& 
Technology.2005,7 
665