针对点目标的抛物线运动，提出了一种使用已标定单目摄像机测量点目标三维坐标的新方法。算法分三个步骤：通过计算悬垂直线在摄像机平面上投影直线的交点得到重力方向的消失点；使用Sampson近似计算抛物线运动轨迹的投影二次曲线，并利用抛物线的射影几何性质计算抛物线支撑平面的旋转矩阵；通过地平面的单应矩阵计算世界坐标系和摄像机坐标系之间的平移矢量，以得到抛物线支撑平面的单应矩阵，并确定抛物线运动点目标的三维坐标。通过仿真实验和真实实验证明了算法的正确性和可行性。实验结果表明：所给出的方法对点目标的抛物线运动测量具有易于实现、测量简便的优点。

Under the assumption of known intrinsic parameters, a novel monocular measurement method consisting of three stages is proposed for point target with parabolic motion. The gravity direction vanishing point is gained by computing the intersection of lines obtained by projecting the hanging lines in the image plane. The conic obtained by projecting the parabolic trajectories is computed using Sampson approximation and the rotation matrix could be evaluated by using parabolic projective geometry properties. By computing the translation vector from world coordinate to camera coordinate using ground planar homography, the parabolic supporting planar homography is established and the three-dimensional (3D) coordinate of point target is determined. Experiments with simulated data as well as with real images show that the method is valid and feasible. The experimental results indicate that the proposed novel approaches are practical and simple.