全球定位系统（GPS），姿态测量（惯性导航系统（INS））和激光扫描测距技术集成的直接空对地定位系统是近年来遥感与测绘领域发展起来的新型定位技术，是定量化三维遥感中获取地面几何信息和生成数字高程模型的主要新技术手段之一。该文给出了该系统的精确定位方程，分析了误差源对定位精度的影响，并给出了数量级评估。结果对实际应用具有重要的参考价值。

Direct space ground positioning system which is composed of Global Positioning System (GPS), attitude measurement (i.e. inertial navigation system, INS) and laser scanning ranging is a new positioning technique developed in recent years, the system is one of the new methods which obtain geometric information of the terrain and generate digital elevation model for quantily of three dimensional remote sensing. This paper gives rigorous positioning equation and error transfer equation of air to ground positioning for airborne and space borne remote sensing. Error analysis of the system and precision evaluation based on the obtained equations for line scanning and circle scanning are given. The simulation computation indicates that the results of this paper have importance to practical application.