Some Investigations of Image Orientation in Aerial Photogrammetry

Abstract

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 photogrammetry.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.