Browsing by Author "Adams, L P"

Now showing 1 - 4 of 4
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    A near real time photogrammetric PC based system to study regional body surface motions of human beings during respiration
    (1990) Gutschow, Barbara Anne; Adams, L P
    The purpose of this thesis was to develop a near real time photogrammetric PC based system to study the regional body surface motions of human beings during respiration. By being able to measure the body surface motion of the human torso during breathing it is possible to evaluate the respiratory muscle functions, i.e. the functions of the diaphragm and intercostal muscles, the only skeletal muscles that are essential to life and which enable us to breathe. Previous studies in this field over the past years have successfully employed stereophotogrammetric analysis. The traditional photogrammetric method however was very time consuming in that it involved the taking of stereo pictures with 35mm cameras, developing the negatives and measuring them in a stereocomparator. The time factor involved severely restricted the research to physiologic studies. For the study to be expanded so that it could be used as a diagnostic tool in the hospital ward environment the time to obtain the necessary results had to be considerably reduced and simplified. A near real time photogrammetric PC based system had to be designed to replace the traditional photogrammetric method. A near real time system was developed for capturing dynamic pictures of the breathing cycle of the patients using a pair of video cameras, a two channel split screen vision mixer and a video cassette recorder with digital storage, all mounted on a custom built hospital cot for easy use in the hospital ward. The images to be measured are selected by viewing the split screen in dynamic stereoscopic mode and selected images are captured on an IBM personal computer equipped with an image processing card. A computing package called TAG has been designed for easy use by non-photogrammetric personnel to evaluate stored images. TAG guides the user through the different processing stages from connecting the video machine to the IBM computer, transferring the selected images, measuring control and object points on the images, and processing the data.
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    Relative orientation with limited control in close range Photogrammetry
    (1982) Rüther, Heinz; Adams, L P
    In close-range photogrammetry, situations can arise in which it is difficult or impossible to establish a network of control points as required for a conventional absolute orientation procedure. The thesis investigates the replacement of the traditional control network by a few control distances measured between well-defined artificial markers or natural feature points. The measured distances must then serve to reduce deformations suffered by the photogrammetric model in the orientation procedures. All investigations are based on analytical rather than analogue photogrammetry. After a review of the concepts of rotation matrices, least squares adjustment and the generation of synthetic image co-ordinate observations, the study is executed in three major steps. A test field of high precision is established by means of space intersection and a camera calibration method for close-range cameras is developed which combines perspective projection with geodetic observations of the lens system parameters. Thus a problem inherent in many camera calibration methods, namely the exact determination of the perspective centre, is largely overcome. Deformation characteristics related to error in elements of interior and relative orientation are determined by the controlled introduction of errors into these elements. The deformations are presented in tabular and diagrammatical form. An analysis of the deformation leads to the conclusions of theoretical and practical relevance for close-range photogrammetry. As a result of the deformation analysis mathematical models are introduced which utilise the measured distances for the reduction of model deformations. The efficiency of homogeneous scaling, affine scaling and convergency correction, as applied individually and in various combinations, is tested. A mathematical formulation of the converging correction as a restraining condition in a least squares adjustment is developed for this purpose. It is shown that a convergency error is less relevant to close-range photogrammetry than generally assumed and that characteristic model deformations in close-range photogrammetry have the character of affine scale errors. Throughout the thesis algorithms are developed which make it possible to execute all computations on computers with limited memory capacity. A program sample for the relative orientation adjustment is given in Appendix IV to demonstrate the memory saving techniques. Finally the results of the investigation are applied to the survey of shoulder height of African elephants in their natural habitat. Equipment and field work are described and results reported.
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    A study of breakwater gap wave diffraction using close range photogrammetry and finite and infinite elements.
    (1984) Pos, John Daniel; Kilner, F A; Adams, L P
    In this thesis the diffraction of water waves passing through a gap in a breakwater is investigated experimentally, using close range photogrammetry, and numerically, using finite and infinite elements. The author was particularly interested in validating specific breakwater gap diffraction diagrams given in popular coastal engineering design manuals. Breakwater gap configurations with the following gap width to wave length ratios (B/L ratios) were analysed, both experimentally and numerically, namely: B/L = 1,64; 1,41; 1,2; 1; 0,75; 0,5. These configurations are symmetrical, i.e. both breakwater arms lie on the same straight line. An asymmetrical B/L = 1,64 breakwater gap configuration was also analysed. Previous experimental breakwater gap diffraction investigations are reviewed leading to the conclusion that the reported results are inconclusive due to (1) the relatively poor accuracy with which the wave heights were measured and (2) secondary basin effects which were superimposed upon and thus distorted the pure diffraction phenomena. In the experimental breakwater gap configurations investigated by the author, splitter plates were used to eliminate the reflection problems on the seaward side of the breakwaters, whilst a novel photogrammetric wave height measurement technique was used to measure accurately the wave heights in the entire basin, before they could be distorted by reflecting waves, basin resonance effects, etc. This "infinite basin technique" was used to simulate experimentally and measure the diffraction of a continuous wave train entering an infinite basin via a gap in an approximate totally absorbing breakwater. A number of different photogrammetric wave height measurement techniques based on analogue procedures, the theory of projective transformations, and the theory of the deformed reference plane, are investigated and developed. It was found that the technique based on the projective transformation theory, and in which the plates are analysed using a stereo-comparator linked to a microcomputer, is the most accurate. Using this technique it was found that, with the cameras situated approximately 5 m above the water surface, the wave heights in the basin can be measured with an accuracy of better than 2 mm. The above method, in conjunction with the infinite basin technique, was used to analyse the experimental breakwater gap configurations. The basic linear wave theory is described leading to the derivation of the Helmholtz diffraction equation. The classical diffraction theories for the semi-infinite breakwater and breakwater gap configurations are reviewed and compared. The Better-off refraction - diffraction equation is then briefly derived. A review of previous numerical refraction - diffraction investigations, and also of modern numerical methods for water wave diffraction and refraction-diffraction, is given. This review led to the adoption of the finite and infinite element program "WAVE", developed at the University College of Swansea, to model numerically the experimental breakwater gap configurations. The use of the "WAVE" program to model breakwater gap wave diffraction is novel and certain conceptual problems had to be overcome. Finally, the experimental and numerical diffraction diagrams obtained were compared to analytical diagrams where these were available. The correlation between the finite element and analytical results is excellent. When comparing the experimental and finite element results the general conclusions are : 1) in regions outside the shadow zones the linear diffraction theory is conservative except close to small gaps (B/L ≤ 1); and 2) within the shadow zones the linear theory is not conservative and one will have to allow for non-linear effects such as radiating second-order waves generated at the breakwater tips, and increased wave orthogonal spreading near the gap centre line and subsequent orthogonal bunching in the shadow zones caused by wave steepness differences along the crests. Other conclusions drawn are : 1) the photogrammetric techniques described are the best available for the experimental simulation and analysis of infinite domain diffraction and refraction - diffraction problems; and 2) the finite and infinite element program "WAVE" is a very useful tool for the prediction of wave heights in large harbour basins.
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    A study of ship wave resistance from an analysis of the wave pattern using close range photogrammetry
    (1986) Paterson, Angus John Cawood; Kilner, F A; Adams, L P
    In this thesis the wave pattern generated by a moving ship is investigated experimentally using close range photogrammetry. The author has been primarily interested in validating a new approach in the determination of the wave making resistance of a ship by means of the energy contained within the wave pattern. Secondary considerations were the measurement of the total ship resistance and other dynamically related applications; squat and trim, bow and stern wave profiles and their interactive effects. The proposed theoretical approach in this analysis of the wave resistance from the wave pattern is essentially phenomenological. As a ship proceeds through the fluid, it generates a set of waves radiating from the bow and stern due to the pressure differences along the hull. Energy is needed to maintain this system and is supplied at a constant rate by the ship, this being the energy required to overcome wave-making resistance. If the total change in energy within the wave pattern can be evaluated over a time interval associated with a known ship movement, then the energy difference will be a related to the wave making resistance.