Research On Target Geo-location Technology Of Airborne Camera Based On High Altitude Oblique Imaging

Airborne camera is one of the main photoelectric devices to obtain ground image information in the air.With the development of airborne camera imaging technology,transmission CCD camera is widely used at home and abroad to replace the traditional film camera.Compared with film camera,CCD camera has the advantages of long shooting distance,large shooting range and high image resolution.With the development of airborne photogrammetry,in addition to high-resolution imaging,highprecision target positioning is also one of the important tasks of airborne camera.The purpose of target location is to accurately obtain the geographical location information of remote sensing image,so as to realize target recognition and tracking and regional electronic map making.Complex airborne imaging environment,pose change of camera carrier and terrain fluctuation all lead to high-precision target location of single image for airborne camera with high altitude squint imaging,which is an urgent problem in the field of airborne photogrammetry.This paper discusses the theoretical basis and current research status of existing airborne camera target geo-location algorithms,and systematically studies the target positioning technology.The specific work of this research can be summarized as follows:This article summarizes the advantages and disadvantages of existing positioning algorithms,and briefly introduces the positioning principles of various positioning algorithms.This paper introduces the related theories of homogeneous coordinates required by the target positioning algorithm,gives the homogeneous coordinate transformation formula,establishes the four basic coordinate systems required by the positioning algorithm and gives the relevant coordinate transformation matrix.Based on the concept of distortion rate,a distortion correction algorithm in the positioning process is proposed.This paper discusses the causes of errors in the positioning algorithm caused by image distortion,gives a calculation method for the distortion rate of each point on the camera focal plane,and establishes a distortion correction model according to the target positioning process.In addition to the image distortion caused by the design of camera optical system,the installation and processing errors,atmospheric refraction,scattering,earth curvature and other factors in the actual work will cause the image distortion.In order to solve this problem,this paper presents an algorithm for measuring camera distortion based on overlapping image.The algorithm uses the overlapped images when the camera is actually working for calculation,combined with the distortion correction algorithm,can effectively reduce the positioning error caused by the distortion of the image edge area.By analyzing the structure of oblique airborne camera,a high-precision ground target positioning method based on distortion processing and LOS(line of sight)correction is proposed.The coordinate system transformation matrix of the vibration reduction platform,the correction equation of the inner frame angle,and the correction equation of the origin of the camera coordinate system are established.Combined with the distortion processing algorithm,the ideal LOS pointing straight line equation of the high altitude oblique airborne camera can be obtained,so as to achieve high-precision ground target positioning.A building target detection algorithm based on Yolo V4 algorithm is proposed.The building target data set of oblique airborne remote sensing image is established by using the historical image data of the laboratory.By optimizing the training process,improving the initial parameters and modifying the output parameters,the building target data set can meet the needs of the target localization algorithm.The recall rate of the optimized detection algorithm can reach 89.02,which can realize the automatic detection of buildings in aerial remote sensing images and give the coordinates of the prediction box in the image coordinate system.Based on coordinate decomposition,a building target location algorithm is proposed.On the basis of building target automatic detection,the longitude and latitude of the target are determined by base point selection,and the height of the target is estimated by image information.Compared with the traditional location algorithm,this algorithm can improve the location accuracy of building target by 30%-50%.The accuracy of target location algorithm is simulated and analyzed by Monte Carlo method.The simulation results show that the image distortion and the target height error have an important influence on the accuracy of target positioning.In the simulation environment,when the image distortion rate of the projection point is 0.06,the error caused by the distortion accounts for about 20% of the total error.When the target height of the building is 50 m,the positioning error caused by the target height can reach about 45%.By selecting the appropriate position and orientation system(POS),angle encoder and processing chip,the positioning module is designed.The actual flight test and remote sensing image experiment prove the effectiveness of the algorithm.Experimental results show that,compared with the traditional positioning algorithm,the two algorithms can improve the overall target positioning accuracy by 20%-50%.In summary,this paper through the research on the target location technology of high altitude oblique imaging airborne camera,based on the existing research results,this paper solves some problems ignored by the traditional algorithm,and integrates image distortion processing,Los correction,and target detection into the target geolocation algorithm,which effectively improves the positioning accuracy of ground targets and building targets,and has great significance to the field of aerial photogrammetry,especially the development of target positioning technology.