Research On Imaging Model And Geometric Calibration Method For Airborne Long Focal Wiskbroom Camera

The airborne long facal oblique camera adopts a wide depth-of-field imaging across the flight direction with large angle linear array wiskbroom,which significantly improves the efficiency of aerial remote sensing on ground observation.It plays a unique role in cross-border observations in the border areas and airborne side-view reconnaissance.However,its complex imaging methods have brought great difficulties to the geometric processing of images.The foreign research results are rarely publicized,and there is a relative lack of domestic research on related technologies.At present,the geometric processing technologies of the linear array of push-broom images have made great progress and tend to be mature.For linear array wiskbroom image,due to its own geometric imaging characteristics,the traditional linear array push-broom image geometry processing theory and technology are no longer applicable.The establishment of geometric processing models and verification of methods have become an urgent need.This thesis focuses on the imaging model construction,imaging simulation and error analysis,geometry calibration and image geometry correction of the linear array wiskbroom camera,aiming to form a complete theoretical model and method for the linear array wiskbroom camera geometry processing.The investigated models,methods and algorithms can not only offer theoretical and technical support to airborne linear wiskbroom camera applications,but also can provide reference for the designment of similar cameras.The main research contents and innovations are as follows:1.Based on the analysis of the structure and imaging methods of airborne long facal oblique cameras and comparison of their differences with linear array push-broom camera imaging,the characteristics of long-distance,large-angle,across flght direction scanning imaging are discussed.The definitions and transition relations between various spatial coordinates of linear wiskbroom camera are discussed,and the strict geometric imaging model of the camera is constructed,and the accuracy of the model is verified through a single image positioning simulation experiment,laying a mathematical foundation for camera geometry calibration and image geometry correction.2.According to the strict imaging model of airborne long facal oblique camera,combined with the platform motion and wiskbroom imaging mechanism,the method of generating the simulation image is studied.Due to the large imaging angle of airborne long facal oblique camera,the problem of iterative non-convergence is easy to occur in the calculation of image projection coordinates during the simulation process.An image vector segmentation iteration algorithm for image coordinate projection is proposed to generate complete and flawless simulation image,providing the basic data for subsequent geometric accuracy assessment and validation of the algorithm for geometric processing.Aiming at the problem that the airborne long facal oblique image has large geometric deformation and is difficult to match with the orthophoto image with high accuracy,a terrain-guided control information acquisition method is proposed and implemented,and the ground control reference required for camera geometry calibration is solved.3.The influence on the geometric positioning accuracy of error sources such as position measurement error,attitude measurement error,and optical system error are quantitatively analyzed,and compared and verified by simulation analysis and theoretical analysis.Due to the two-dimensional motion of the scanning mirror in the imaging process of the airborne long facal oblique camera,the calibration model is complex,there are many installation parameters,and the correlation is serious.The same parameters are effectively combined and simplified,and the code disc observed value is introduced as a constant into the geometry calibration model.The correctness of the method was verified by experiments.4.According to the strict imaging model and system error rule of the camera,the geometric calibration model is established.Taking into account the physical model of the camera's interior orientation,a pointing angle geometry calibration model based on the scan mirror coordinate system is proposed and constructed.The solution to the calibration model parameters is designed.The correctness of the calibration model and the effectiveness of the solution are verified through experiments.5.The key problem of linear array image geometric correction based on strict model is the search of the best scanning line.The traditional method has low searching efficiency,and the object-based geometric constraint method is not suitable for linear wiskbroom images.Therefore,a geometric correction method for linear wiskbroom image is proposed,which uses the constraints of the spatial relationship between features.The correctness and computational efficiency of the method are verified by experiments.