Study On The Method Of Photogrammetry Of Large-scale Target Based On Airborne Vision

In the application of industrial measurement,photogrammetry is usually used to measure the size,shape and position of large targets.However,in the photogrammetry of super large-scale targets such as radio telescope antenna,power tower and so on,measuring personnel takes pictures with the aid of lift trucks or other platforms.It has low measurement efficiency and a certain danger.To solve this problem,a research on the method of large-scale targets photography based on airborne vision is made,with UAV's advantage of maneuverability.First of all,the overall scheme of the research is set up according to the technical requirements,and the hardware and software structure of the airborne visual photogrammetry system is designed in this paper.On this basis,components are selected,UAV photogrammetry platform is constructed and camera calibration is accomplished with Zhang Zhengyou plane calibration method.To solve the problem that the surface features of the large target are difficult to be extracted and matched,coded and non-coded targets is used as the auxiliary feature points in the paper.In order to improve the recognition accuracy of coded targets,a coding band recovery algorithm based on affine transformation and morphological processing is proposed,and the recognition result of the algorithm is verified by experiments.At the same time,the algorithm of center positioning is studied and a comparative analysis of various methods is carried out through simulation experiments and the sub-pixel location of feature point's center is realized.Aiming at the problem of auto orientation of single image,a space resection algorithm based on four non-collinear coded targets is studied in this paper.Based on single image orientation,a multi-image auto orientation strategy is formulated.In order to improve the matching accuracy of non-coded targets,a matching method based on polar line constraints is proposed.The experimental results show that the method achieves high accuracy through matching three images.After solving the three-dimensional coordinates of all the targets,the accuracy of the whole calculation is improved by the beam adjustment.Finally,the feasibility and accuracy of airborne photogrammetry are verified through field measurement,and the measurement error of the system is analyzed.