Research And Practice Of Digital Industrial Photogrammetry

Domestic manufacturing industry has been increasingly depending on the precise photogrammetric measurement during its development. The dissertation summarized characters and development trends of typical photogrammetry systems at home and abroad. The research included both hardware and algorithms. A series of innovative technologies and their applications in engineering projects were presented. Primary coverage of the dissertation was as follows:(1) Two kinds of typical coded targets and their design principles were introduced. A new set of dot-distributed coded target with code capacity of 496 was designed, which can be decoded automatically with the invariant of cross ratio.(2) A new device for orientation composed of a ring target and five circle ones were designed. Its decoded algorithms were also researched.(3) Both principles and performances of image sensors CCD, CMOS and scientific CCD were introduced. Influence factors of measurement accuracy in digital cameras such as resolution, imaging noises and distortions were analyzed. The principles for choosing digital cameras were presented.(4) Camera calibration experiments were carried out with three distortion models commonly used, which are polynomial model, ten-parameter model and finite element model. A new combined calibration method based on ten-parameter model and finite element model was presented. Calibration experiments showed that it can improve the precision of metric cameras dramatically.(5) Distribution regularities of gray scales in images of circle retro-reflective targets were analyzed. Several recognition and centring algorithms for target images were introduced. A new centring algorithm based on the edge searching and the intensity-weighted centroiding was presented, whose positioning error proved to be less than 0.02 pixels.(6) Images of circle retro-reflective targets were simulated with the image defocusing model. Experiments were carried out on the accuracies of different methods with simulation images, which showed that the intensity-weighted centroiding algorithm is much more precise than the ellipse fitting algorithm.(7) Ellipse image eccentric errors of targets on different objects were researched quantitatively with simulation images. Target radiuses and station parameters were calculated for the plane, spherical and cylindrical objects.(8) Elements of exterior orientation for one single image were calculated with space resection based on four non-collinear control points, while those for multiple images were calculated with the device for orientation and coded targets. Experiments proved the orientation method is effective.(9) The epipolar line matching method of corresponding image points was introduced. A new matching method based on known points and the epipolar line constraint was presented to improve the errors of epipolar line constraint, which proved effective.(10) Simplified solution of normal equation was deduced for the self-calibrated bundle adjustment. The length standard of the measurement coordinates was defined with several reference rulers. Blunders were detected with the residual errors of image point coordinates and the numbers of redundant observations.(11) The digital industrial photogrammetry system named MetroIn_DPM developed base on the research of the dissertation was introduced, whose measurement accuracy proved as high as V-STARS. The MetroIn_DPM system was applied in the measurements of one antenna during its assembly process and the other in several working positions.