Human motion analysis is one of the active research areas in computer vision. The trend shifts from computing motion fields to determining actions. We present an action coding scheme based on a trajectory of features defined with respect to a part based coordinate system. The method does not require prior human model or special motion capture hardware. The features are extracted from images segmented in the form of silhouettes. The feature extraction step ignores 3D effects such as self occlusions or motion perpendicular to the viewing plane. These effects are later revealed in the trajectory analysis. We demonstrate preliminary experiments.