A method for detecting objects that are moving with respect to the ground from a pair of stereo rectified images, the method, performed by a motion detection engine, characterized by the method comprising: receiving a pair of stereo rectified images comprising two images taken by one sensor on a moving aircraft at different times (P1, P2) and stereo rectified to form the pair of stereo rectified images that are oriented perpendicular to a stereo baseline and parallel to each other; for each feature in one of the stereo rectified images, associating a subject feature with the same feature in the other stereo rectified image to form a feature association; for each feature association, forming a feature motion track following the subject feature association from one of the stereo rectified images to the other stereo rectified image, wherein the feature motion track is indicative of movement of the subject feature; and differentiating feature motion tracks that are non-parallel to the stereo baseline (130; 200) from other feature motion tracks (205-230, 240) that are parallel to the stereo baseline (130; 200), wherein the differentiated feature motion tracks represent detected objects moving with respect to the ground; wherein differentiating the feature motion tracks includes, for each feature motion track formed, calculating the slope of a subject feature motion track with respect to the stereo baseline (130; 200); and identifying the feature motion track to be parallel to the stereo baseline (130; 200) when the calculated slope of the motion line of the feature motion track with respect to the stereo baseline (130; 200) is zero; and identifying the feature motion track to be non-parallel to the stereo baseline (130; 200) when the calculated slope of the motion line of the feature motion track with respect to the stereo baseline (130; 200) is non-zero. receiving a pair of stereo rectified images comprising two images taken by one sensor on a moving aircraft at different times (P1, P2) and stereo rectified to form the pair of stereo rectified images that are oriented perpendicular to a stereo baseline and parallel to each other; for each feature in one of the stereo rectified images, associating a subject feature with the same feature in the other stereo rectified image to form a feature association; for each feature association, forming a feature motion track following the subject feature association from one of the stereo rectified images to the other stereo rectified image, wherein the feature motion track is indicative of movement of the subject feature; and differentiating feature motion tracks that are non-parallel to the stereo baseline (130; 200) from other feature motion tracks (205-230, 240) that are parallel to the stereo baseline (130; 200), wherein the differentiated feature motion tracks represent detected objects moving with respect to the ground; wherein differentiating the feature motion tracks includes, for each feature motion track formed, calculating the slope of a subject feature motion track with respect to the stereo baseline (130; 200); and identifying the feature motion track to be parallel to the stereo baseline (130; 200) when the calculated slope of the motion line of the feature motion track with respect to the stereo baseline (130; 200) is zero; and identifying the feature motion track to be non-parallel to the stereo baseline (130; 200) when the calculated slope of the motion line of the feature motion track with respect to the stereo baseline (130; 200) is non-zero.