Morgado, Ana M. de O.; (1996) Automated Procedures for Orientation of Digital Images. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The most recent development in photogrammetry is the evolution from analytical (film-based imagery) to digital (pixel-based imagery) photogrammetry. Advances in computer and sensor technology have contributed to the present transition from analytical stereoplotters to digital processing systems or digital workstations. Digital Photogrammetric Workstations are under development with intensive study still taking place on the algorithms to be included. This study begins with an analysis of the potential of digital photogrammetry to substitute for and/or support the more traditional photogrammetric methods. The consequent evolution of the digital photogrammetric instrument was investigated. Considering that the main aim of digital photogrammetry is to automate the various photogrammetric processes it was found that although digital photogrammetry already offers a considerable degree of automation, this is a subject still under development. Determination of the orientation of the camera at the moment of exposure is a necessary step in the measurement process with most photogrammetric processes being based on the oriented model. The traditional photogrammetric orientation method, divided into the three orientation problems: interior, relative and absolute orientation, was followed. After an analysis of different methods of image acquisition and an assessment of the performance of the Sharp JX-600 scanner (the device used in this study to acquire the digital image) each one of the orientation problems was investigated. The emphasis was on the automation of the measurements to be used in each case. Interior orientation automation of corner fiducials photography, non-metric photography and reseau photography was performed and the results obtained were compared with the ones obtained from manual measurements. Two methods of accomplishing automatic relative orientation were analysed. The strategy adopted is based on the pyramidal matching technique performed in 6 windows sectioned from the image at the 6 Van Gruber positions. Automatic absolute orientation is a more complicated process to automate than the previous two. After an outline of the problems involved and a summary of some of the techniques that have been considered to solve them, a detailed description of the two methods adopted to automate absolute orientation is presented. These two methods to relate the map to the image are based on the dynamic programming technique and on similarity tests on the shape of common features. The complete orientation process linking the three problems is finally performed, resulting in a complete strategy to automatically obtain the orientation parameters.

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