Bibliography: pages 133-156. / The deep-level gold mines on the Witwatersrand (South Africa) are located at depths of over 3,000m below surface. Mining excavations follow tabular reefs that are kilometres in extent, but only a few centimetres thick. Due to the great depths of these excavations and the large overburden of rock, immense pressure is exerted on the rock mass being excavated. In order to relieve this stress in the rock mass being mined, the rock is "pre-conditioned" by pre-fracturing the rock face with large blasts. This has the effect of pushing the critical stress load further into the rock mass, thus increasing safety at the rock face. To better understand the rock behaviour as a result of by pre-conditioning blasts, it is desirable to quantify the deformations of the rock face. Digital photogrammetry provides an ideally suited method of monitoring these deformations, as the necessary equipment is portable and easy to use underground, where the conditions are extreme with temperatures approaching 40°C and humidity levels close to 100%. Digital photogrammetric techniques are also highly accurate, and can be used to detect relatively small three-dimensional movements. The determination of the three-dimensional (XYZ) co-ordinates of the rock face, represented by densely spaced individual points, by means of digital photogrammetric techniques, is reported in this thesis. The novel measurement system developed comprises the following components: * establishment of a stable reference co-ordinate system; * image acquisition; * camera calibration and exterior orientation calculation; * feature extraction; * multi-image matching and space intersection; and * surface modelling. The details of the techniques developed and implemented in order to generate the necessary object space co-ordinates are discussed. Sub-millimetre accuracy point determination, as required for deformation analysis was achieved and a sample of the underground test result data is presented. The final analysis of the underground test data made it apparent that digital photogrammetry is highly suitable for the determination of digital terrain models of the rock surfaces, for subsequent deformation analysis. The relative speed of the process and the convenient size of the equipment makes the technology especially suitable to the demanding underground mining environment. The difficulties, which were experienced as a result of the highly restrictive environment, were overcome through careful planning and pre-analysis. It can thus be concluded that this approach is not only feasible, but it meets the stringent demands of the underground mining industry, as is confirmed by the high accuracy of the final surface point co-ordinates achieved. In addition to being implemented in the underground mining industry, the measurement system developed was used for the mapping of several other textured surfaces. In particular it was used in mapping the 3.6 million-year-old hominid trackway located at Laetoli (Tanzania), the imprints of cheetah and rhinoceros for the purposes of conservation, and for the archaeological documentation of a shipwreck found off the Cape coast (South Africa). All of these applications are discussed and the results achieved presented.

Bibliography: p.187-193. / The maintenance and expansion of piping systems of petro-chemical plants is a complex and costly process. These costs can be reduced by knowledge of the as-built dimensions and layout of the piping system. As-built Computer Aided Design (CAD) models of such piping systems, specifically the use of Plant Design System (PDS) software packages, allow for more efficient planning than paper plans. Conventional surveying and analogue photogrammetry have been methods that have traditionally been used to capture the necessary CAD information. More recently, the Department of Geomatics at the University of Cape Town has produced software which replicates the analogue photogrammetric approach using digital images (Cammidge, 1996). The objective of this thesis is to develop a pipe measurement technique which can supplement those currently being used and overcome some of their shortcomings. A further objective is to present an overview of the pipe measurement techniques, photogrammetric principles, image processing techniques and programming considerations which would be required to develop a robust, fully functional, pipe measurement software package integrated with a PDS. The author hopes that this thesis will form the foundation for the development of such a software package for local and possibly international industry. A digital photogrammetric technique related to line photogrammetry is developed. This technique makes use of lines in an image which represent the silhouette edges of the cylinder. The use of photogrammetry based on lines avoids some of the shortcomings of conventional point-based photogrammetry. It is not necessary to identify conjugate points in images, nor is it even necessary for overlapping images of the cylinder to be captured. Furthermore, this thesis reports on a number of tests designed to gauge the developed techniques' accuracy and suitability for use in pipe metrology in an industrial plant. The techniques were found to be capable of achieving results which deviated by, on average, 2-3mm in object position and 0.1° in direction from the likely true values of the cylinder axis. The radius could be determined to better than 1 mm. The techniques developed here proved to be suitably accurate for the purpose of determining the parameters of pipes in industrial plants. However, certain factors may reduce the accuracy and these are also discussed. This thesis concludes that a novel digital photogrammetric technique for measuring pipes in an industrial plant was successfully developed. Recommendations are made as to how the technique might be improved to allow sub-millimetre accuracies to be obtained. Finally, a recommendation is made that the information contained within the thesis be used as the basis for designing a digital photogrammetric measurement module to be linked to a PDS.

Throughout history, cultural institutions like the Iziko Museums of South Africa have preserved, catalogued, researched and displayed a diverse collection of cultural objects. The renewed interest in digital media has revived the move to reclaim cultural identities, bringing with it the associated challenges regarding the veracity of historical accounts. With the transition to digitisation, and the adoption of digital curatorship for knowledge production in museum environments, it has become necessary to examine the historical accuracy, reliability and trustworthiness of the digital information being provided. Digitisation is an important priority for most cultural institutions. This study contributes to the colonial debate about museum classification and the challenges that these institutions face regarding what is referred to as the “unknown maker”. The use of the term “unknown maker(s)” to denote creators of cultural objects housed in the Iziko South African National Art Gallery collections was crucial to this investigation into the digital cataloguing of objects whose creators could not be determined. The findings show that a national museum is a space where identities are contested, and that museum professionals are repeatedly faced with difficult curatorial and ethical decisions when it comes to classifying cultural objects. As a result, the problems encountered with the digitsation and cataloguing of cultural objects are extensive. Inaccurate classification processes, including the use of the term “unknown maker(s)”, affects how digital heritage objects are recorded, the servicesthat museums offer, how exhibitions are presented, the research that is undertaken, and the skills required to manage cultural objects.

This thesis comprises of five chapters. Chapter one describes basic principles of the digital image, digital image construction and the present status of the digital photogrammetry system, named PHOENICS (PHOtogrammetric ENgineering and Industrial digital Camera System), as developed by H. Rüther (1989). The target's shape analysis in the digital image are presented in chapter two. Chapter three presents the algorithms to detect and locate target on the digital image. These are the least squares adjustment technique, moment method, moment-preserving for edge detection as well as test methods for the evaluation of the various alglorithms. The novel RG method is presented in chapter four. Chapter five introduces the theory of some image processing methods.

Bibliography: pages 122-132. / This thesis reports on the investigation, development and implementation of digital/photogrammetric algorithms into a compatible system for measuring surfaces. Each of the important stages of such a measurement are dealt with in the text. Specifically, these include camera calibration, free network adjustment, location and centering of circular targets, orientation determination, the matching and measuring process and handling of results. The chosen algorithms (existing, modified and/or developed in this work) were all incorporated/designed to form an efficient and usable surface measurement system. Of particular importance was the investigation of determining conjugate (matching) surface points in the multiple images. In this respect a novel multi-image correlation search procedure was designed, implemented and tested. This algorithm provides high accuracy matching methods with suitably close provisional matching positions. A series of tests was carried out to study the performance of the algorithm and the results are presented in this work. Most notable was the method's high reliability when using more than two images, even in image areas with highly repetitive patterns. Multi-image correlation is considerably more robust than "traditional" stereo-correlation procedures. Other system tests performed included: tests on the stability of projected light from two off-the shelf projection devices; a test on the effect of PLL synchronisation of the camera-framegrabber combination of the images; tests on the accuracy performance of different centering techniques and surface measurements themselves. It was found that the off-the-shelf slide projector tested did not provide a stable projection, however an overhead projector which was warmed up for over an hour provided a suitably stable projection. The PLL synchronisation of the camera-framegrabber system produced a noticeable line-jitter (between sequential images) reaching over 0.1 pixels in the most badly affected lines. In a simulated test with artificial targets, template matching obtained the most accurate centre coordinates, however the much faster weighted centre of gravity with grey value as weight technique also provides highly accurate results. These two centering techniques agreed to 1/100th of a pixel when centering with real targets. The much faster centroiding technique is thus highly recommended for any application which requires high processing speeds (such as with on-line systems). Surface measurement precisions of 5/100th mm in the plane of the surface and 15/100th mm in depth were achieved in the measurements of the test objects. These objects all had similar dimensions with a diagonal of about 250mm in length. These accuracies could be substantially improved with higher resolution cameras and more images. Together, the algorithms presented in this work formed a surface measurement software program. The success of many of these algorithms, such as the target location method, and the semi-automatic point identification and exterior orientation determination procedure, could not be gauged with results as such, but by their successful incorporation into the system as properly functioning units.

Bibliography: p. 66-68. / Photogrammetry has many inherent advantages in engineering and industrial applications, which include the ability to obtain accurate, non-contact measurements from data rapidly acquired with the object in situ. Along with these advantages, digital photogrammetry offers the potential for the automation or semi-automation of many of the conventional photogrammetric procedures, leading to real-time or near real-time measurement capabilities. However, all-round surface measurement of an object usually benefits less from the above advantages of photogrammetry. To obtain the necessary imagery from all sides of the measurement object, real-time processing is nearly impossible, and it becomes difficult to avoid moving the object, thus precluding in situ measurement. However, all-round digital photogrammetry and, in particular, the procedure presented here, still offer advantages over other methods of full surface measurement, including rapid, non-contact data acquisition along with the ability to store and reprocess data at a later date. Conventional or topographic photogrammetry is well-established as a tool for mapping simple terrain surfaces and for acquiring accurate 3-D point data. The complexities of all-round photogrammetry make many of the standard photogrammetric methods all but redundant. The work presented in this thesis was aimed at the development of a reliable method of obtaining complete surface data of an object with non-topographic, all-round, close-range digital photogrammetry. A method was developed to improve the integrity of the data, and possibilities for the presentation and visualisation of the data were explored. The potential for automation was considered important, as was the need to keep the overall time required to a minimum. A measurement system was developed to take as input an object, and produce as output an accurate, representative point cloud, allowing for the reconstruction of the surface. This system included the following procedures: ■ a novel technique of achieving high-accuracy system pre-calibration using a cubic control frame and fixed camera stations, ■ separate image capture for the control frame and the object, ■ surface sub-division and all-round step-wise image matching to produce a comprehensive 3-D data set, ■ point cloud refinement, and ■ surface reconstruction by separate surface generation. The development and reliability of these new approaches is discussed and investigated; and the results of various test procedures are presented. The technique of system pre-calibration involved the use of a mechanical device - a rotary table - to impart precisely repeatable rotations to the control frame and, separately, the object. The actual repeatability precision was tested and excellent results achieved, with standard deviations for the resected camera station coordinates of between 0.05 and 0.5 mm. In a detailed test case, actual rotations differed from the desired rotations by an average of 0.7" with a standard deviation of less than 2'. The image matching for the test case, from a set of forty-eight images, achieved a satisfactory final accuracy, comparable to that achieved in other similar work. The meaningful reconstruction of surfaces presented problems, although an acceptable rendering was achieved, and a thorough survey of current commercially available software failed to produce a package capable of all-round modelling from random 3-D data. The final analysis of the results indicated that digital photogrammetry, and this method in particular, are highly suited to accurate all-round surface measurement. The potential for automation - and, therefore, for near real-time results - of the method in the stages of image acquisition and processing, calibration, image matching and data visualisation is great. The method thus lends itself to industrial applications. However, the need for a robust and rapid method of surface reconstruction needs to be fulfilled.

Bibliography: p. 212-220. / The aim of digital photogrammetry is the automated extraction and classification of the three dimensional information of a scene from a number of images. Existing photogrammetric systems are semi-automatic requiring manual editing and control, and have very limited domains of application so that image understanding capabilities are left to the user. Among the most important steps in a fully integrated system are the extraction of features suitable for matching, the establishment of the correspondence between matching points and object classification. The following study attempts to explore the applicability of pattern recognition concepts in conjunction with existing area-based methods, feature-based techniques and other approaches used in computer vision in order to increase the level of automation and as a general alternative and addition to existing methods. As an illustration of the pattern recognition approach examples of industrial applications are given. The underlying method is then extended to the identification of objects in aerial images of urban scenes and to the location of targets in close-range photogrammetric applications. Various moment-based techniques are considered as pattern classifiers including geometric invariant moments, Legendre moments, Zernike moments and pseudo-Zernike moments. Two-dimensional Fourier transforms are also considered as pattern classifiers. The suitability of these techniques is assessed. These are then applied as object locators and as feature extractors or interest operators. Additionally the use of fractal dimension to segment natural scenes for regional classification in order to limit the search space for particular objects is considered. The pattern recognition techniques require considerable preprocessing of images. The various image processing techniques required are explained where needed. Extracted feature points are matched using relaxation based techniques in conjunction with area-based methods to 'obtain subpixel accuracy. A subpixel pattern recognition based method is also proposed and an investigation into improved area-based subpixel matching methods is undertaken. An algorithm for determining relative orientation parameters incorporating the epipolar line constraint is investigated and compared with a standard relative orientation algorithm. In conclusion a basic system that can be automated based on some novel techniques in conjunction with existing methods is described and implemented in a mapping application. This system could be largely automated with suitably powerful computers.

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This paper studies the activity of bipedal walking with the objective of describing procedural techniques to automate this process. The main problem this paper explores is how to mathematically characterize the relationships and motion of different limbs involved in the process of walking and to represent realistic and natural walk cycles. Other issues discussed are possible variations to create different types of walk cycles. The results have been used to implement and develop a learning tool to assist students in the creation of animated walk cycles. This paper is reporting on the methods used to create a practical computer-assisted tool to show and teach students how walk cycles get affected by different parameters without having to learn every facet of their complicated 3D animation applications. The results can also be applied to many different areas of visualization, such as architectural and virtual reality environments, where human or bipedal models are involved.