研究了面向数字地球的虚拟现实系统关键技术，提出了多层场景引擎（MLSE）、视点相关动态多分辨率地形模型（VDDMTM）和ActiveX构件网络模型。MLSE采用层机制集成多元数据，实现场景绘制和交互。VDDMTM基于四叉树表示多分辨率地形，并结合多分辨率纹理映射，根据视点位置对大规模地形实时简化，既提高了场景绘制速度，又保留了视点相关细节。网络模型采用基于Client/Server结构的ActiveX构件方案，既满足数字地球的建模特性，又支持标准的WWW浏览器。在此基础上开发了一个面向数字地球的原型系统－虚拟地球系统VES（VirtualEarthSystem），并用于虚拟永定河和喜马拉雅山。

This paper addresses several key issues for digital earth oriented virtual reality system, with multi layer scene engine (MLSE), view dependent dynamic multiresolution terrain model(VDDMTM), ActiveX component based network model discussed. By means of scene layer, MLSE enables multi variates integration, scene rendering and user interaction. Quad tree structure is used for multi resolution terrain representation. View dependent terrain simplification and multi resolution texture mapping are applied to keep ROI(Region of interest) details and accelerate rendering. Client/Server based ActiveX network model not only meets specific needs for geo data modeling, but also well supports WWW browsers. Based on above research, a prototype system, virtual earth system(VES), was developed to visualize YongDing River and Mountain Himalayan.