Huang, Yi Dong; (1994) Three dimensional measurement based on theodolite-CCD cameras. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis concerns the investigation of the fundamental problems of three dimensional measurement using the theodolite-CCD camera, which is formed by attaching a CCD camera rigidly to the telescope of a theodolite. A novel method – the camera-on-theodolite method – is proposed for the calibration of the theodolite-CCD camera. This method is also applicable to the calibration of any other cameras that can be mounted on the telescope of a theodolite. The most significant advantage of this method over previous ones is the dispensability of control target fields. The effectiveness of the method is proved with both simulation and experiments. Computer software is produced for implementing the new method in routine CCD camera calibration and is proved by experiments to be efficient. Algorithms are designed and computer programs produced for automatic location of circular target images to subpixel accuracy. The algorithms involve parabolic interpolation of gradients at edge points of target images followed by least squares fitting of the edges with ellipse. The accuracy of target image location achieved by the algorithms is assessed using three methods developed by the author and is found to be as high as 1/50 pixel. One of the most important measuring functions of theodolite-CCD cameras – theodolite scanning photogrammetry – is investigated in which a long focus lens is used to take images at large scale serially in grid form to cover the measured object. It is shown with experiments that this function can either improve the accuracy of CCD cameras in object coordinate determination for a specified object coverage or increase the object coverage of the CCD cameras for a specified accuracy in object coordinate determination.

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