A model-based approach is presented that assumes locally constant angular momentum (LCAM). The model constrains the motion, over a local frame subsequence, to be a superposition of precession and translation. The trajectory of the rotation center is approximated by a vector polynomial. The nature and parameters of short-term motion can be estimated continuously with the goal of understanding motion through the image sequence. Noise smoothing is achieved by overdetermination and a least-squares criterion. Based on the assumption that the motion is smooth, object positions and motion in the near future can be predicted, and short missing subsequences can be recovered.