According to the theory of vanishing point, a novel approach to calibrate the beresight misalignment of airborne position and orientation system（POS） based on photo nadir point is proposed. First, the strict mathematical relationship between the photo nadir point and the boresight misalignment of airborne POS is established and the error equations for solving the boresight misalignment are derived. Then, a set of actual images are tested. The empirical results show that the mathematical model established is correct and the boresight misalignment could be calibrated by using more than two photo nadir points. The proposed method does not need a specific calibration field and ground control points. Therefore, it has practical value to calibrate the boresight misalignment when taking large-scale aerial photography over urban areas with POS.%基于灭点理论，提出一种利用像底点检校机载POS系统视准轴误差的方法。首先从理论上建立像底点与POS系统视准轴误差之间严格的数学关系，并在此基础上推导出求解视准轴误差的误差方程式，然后用一组带有POS数据的航空影像进行了试验验证。试验结果表明，所建立的利用像底点检校POS系统视准轴误差的模型是正确的，用两张以上像片上的像底点坐标即可检校出POS系统的视准轴误差，而毋须布设特定的检校场和地面控制点，对城区大比例尺航空摄影时POS系统视准轴误差检校具有一定的实用价值。
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