This paper introduces a novel geometric constraint to boresight calibration for aerial multi-head camera systems. Using the precise EOPs (exterior orientation parameters) estimated for each physical camera and the surface information of the area of interest, multi head camera provides a synthetic image at each time epoch. The camera EOPs can be computed directly from the navigation solution provided by an onboard GPS/INS system and camera platform geometric calibration parameters, which represent the geometric relationship between the camera heads. For direct acquisition of EOPs from the navigation system, the camera frame and the INS frame should be precisely aligned. Boresight can be defined as mounting angles between the INS frame and camera frame. Since small but unknown misalignment angles could cause large errors on the ground, which suggests that they should be precisely estimated. In this paper, unknown boresight angles are estimated by using camera platform geometric calibration parameters as constraints. Since each physical camera of the multi-head camera system is tightly affixed to the platform, the geometry between camera frames remains constant. Simulation results show that the constrained method provides better estimation in terms of both accuracy and precision compared to traditional approach which does not use the constraint
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