A calculating model based on difference method was proposed to calculate the image motion velocity vector to compensate precisely the image motion of a space camera. Firstly, the earth imaging model was established by utilizing coordinate transformation ,and the relative motion between the image point and the image plane was analyzed in vertical, roll and pitch attitudes according to the states of the image motion. Then, a method was proposed to calculate the image motion velocity vector according to the law of the relative motion between the image point and the image plane. Finally, the proposed method was compared with the coordinate transformation method. The result shows that the error between the two methods is within 0. 1％, which proves the efficiency of this method. The proposed method overcomes the complex compulation from traditional methods and can be used in calculating the image motion velocity vectors for other space cameras.%为了实现空间相机精密像移补偿,提出了一种基于差分法的空间相机像移速度矢量计算模型.首先,应用坐标变换建立空间相机对地成像模型,分析了空间相机在垂直摄影、侧摆摄影和前后摆摄影时,目标像点与成像面之间的相对运动情况.然后,根据目标像点在成像面上的匀速运动规律,提出对像点位置坐标进行差分计算求得像移速度矢量的方法.最后,对提出的方法与基于坐标变换的像移速度矢量计算方法进行了比较.结果表明,两种计算方法的相对误差在0.1%以内,验证了该方法的正确性.该方法避免了传统坐标变换法复杂的微分计算,提高了计算速度,亦可应用于同类遥感器的像移矢量计算中.
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