Study Of High-precision Attitude Measurement Based On Close-range Photogrammetry

Generally speaking, the application range of the close-range photogrammetry is between 1 to 20 meters, but it’s too difficult to operate on practical measuring the attitude of the object about 100 meters away. So the research of a lot of practical problems is taken, such as the calibration of camera’s internal and external parameters, the automatic recognition of cooperative targets, the high-precision extraction of cooperative targets, the high-precision attitude measurement. According to these techniques, a high-precision attitude measurement system is built to achieve the attitude measurement of the target rotating around a fixed point omnidirectional.Considering the difficulty on the calibration of camera’s external parameters over 100 meters away, the focal length is focused on the measured target. After adjusting the control of aperture, clear images are obtained and the calibration of the camera’s internal parameters is completed. A new kind of calibration target rod is designed. Firstly, place it near the photographic measuring instrument. Then obtain the image coordinates and the space coordinates of the cooperative targets on the target rod. At last, the calibration of camera’s external parameters can be completed by the multiplane imaging method, which is presented by Zhang Zhengyou. The parameter model of the camera’s calibration is designed and analyzed. All the influencing factors of the external parameters are obtained. The action effect of each factor is computed in the simulation experiments, and it is validated by the outfield experimental results. According to the actual requirements, the experiment precision requirement of the geodesy coordinates can be put forward.Both the proximal calibration of the camera’s parameters and the distal attitude measurement are analyzed considering that the backgrounds and imaging conditions are different. The scheme of image pre-processing is unified. The bonding method of cooperative targets on the target can be designed by the 3ds Max simulation experiments. According to the research of the targets’ recognition on the combination of the method based on the knowledge with the method based on the invariant, the best extraction method of the cooperative targets and their coding landmarks is excogitated.on the basis of geometrical fitting and the gradual change of the edge of gray image, a ellipse fitting method based on the weighted derivative of gray is put forward. It has been proved that its accuracy could be improved by 0.02~0.03 pixels in the simulation experiments. These techniques make it achievable that real time, the accuracy and the precision meet the requirement.Not only several kinds of mathematical models but also the sparse bundle adjustment algorithm has been further studied. According to the requirements of practical application, such as the calibration of camera’s parameters, ellipse fitting, the establishment of target coordinate, target attitude measurement, the different kinds of mathematical model can be constructed. The accuracy can be increased by designing optimization algorithms.Further study of the mathematical models of monocular measurement and binocular intersection is required. The localization of the calibration target rod and the photographic measuring instrument is done. A combination of the two methods of measurement attitude is proposed, which can be used to measure the target’s attitude during the rotation. The effect of all factors on the accuracy of target’s attitude is analyzed quantitatively. After all datum of the cooperative targets in each camera imaging are fused, the sparse bundle adjustment algorithm can optimized the adjustment. It increases the accuracy of attitude measuring, meanwhile, it meets the real-time requirement, especially during monocular measurement.A combined debugging between the photographic measuring instrument, the sending optical terminal, the receiving optical terminal and the computer is completed. The functions of multifunctional serial cards, image acquisition cards and the lens control card have been tested. The controlling the camera, the lens, the laser and the rotational station is realized, and the commissioning experiments of its accuracy are finished. Lots of experiments are carried out in external field, such as the calibration of cameras internal and external parameters, the simulation verification experiment of cooperative targets with a long distance, the establishment of the target coordinate. The error analysis of the related experimental results is obtained, at the same time the method of the whole system is validated.