航空摄影测量影像定向的若干探讨

Some Investigations of Image Orientation in Aerial Photogrammetry

简要叙述了现行航空摄影测量的作业模式和关键技术要求，分析了直接利用航摄像片外方位元素恢复立体模型所得到的目标点物空间位置精度以及模型点的上下视差。经对带有双频动态GPS数据的1：2500～1：60000各种摄影比例尺的覆盖多种地形航摄像片的试验表明，由摄影测量加密所获取的影像外方位元素可直接用于4D产品生产中的影像定向，而由POS系统提供的影像外方位元素还难以直接用于摄影测量测图。

Aerial photogrammetry is the science and technology for obtaining three-dimensional spatial information about the Earth surface from aerial images. The key point of this issue is the rapid and accurate determination of image＇s position and attitude. This goal is met by aerial triangulation based on well distributed ground control points （GCPs） in conventional photograrmnetry. With the wide application of global positioning system （GPS） and position and orientation system （POS）, image exterior orientation elements can be acquired at the instant of imaging. Therefore, the stereo model reconstitution and direct georeferencing are becoming a new topic in aerial photogrammetry. Aerial triangulation evolves and progresses towards digital mapping without GCPs. This paper describes the operational issues and basic technical requirements of modern aerial photogrammetry. The accuracy of photogrammetric point determination and the y-parallax at corresponding model points are analyzed when stereo models are reconstituted by using the exterior orientation elements of aerial images. Real aerial photographs, at image scales from 1 ： 2 500 to 1 ： 60 000, with POS data taken over various topographic forms in China were processed by our POS-supported bundle block adjustment program WuCAPS. The empirical results verified that the accuracy of the exterior orientation elements from bundle block adjustment met the requirements of the specifications of topographic mapping. However, the accuracy of the exterior orientation elements determined by POS failed to meet the requirements of the specifications of topographic mapping.