关键词: POS系统, 影像外方位元素, 直接对地目标定位, 安置元素航测成图, 精度

Abstract: On the basis of direct georeferencing in POS-supported aerial photogrammetry，the relationship model between accuracy of object points and exterior orientation elements is established according to the error propagation law.The accuracy requirements of exterior orientation elements in topographic mapping are analyzed in theoretically.Four sets of actual aerial photos are used to test；which are at different scale and in different terrain.The empirical results verify that image elements of exterior orientation obtained by a POS can satisfy the accuracy requirements of topographic mapping，no matter which scale and terrain the empirical block is classified to.However，to satisfy the accuracy requirements of object point in elevation，the accuracy requirements of exterior orientation elements are at least one time higher than that in planimetric mapping.

Key words: Position and Orientation System（POS）, exterior orientation elements, direct georeferencing, aerophotogrammetric mapping using image orientation parameters, accuracy