Non-Stationary "Shape Activities"

TitleNon-Stationary "Shape Activities"
Publication TypeConference Papers
Year of Publication2005
AuthorsVaswani N, Chellappa R
Conference NameDecision and Control, 2005 and 2005 European Control Conference. CDC-ECC '05. 44th IEEE Conference on
Date Published2005/12//

The changing configuration of a group of moving landmarks can be modeled as a moving and deforming shape. The landmarks defining the shape could be moving objects(people/vehicles/robots) or rigid components of an articulated shape like the human body. In past work, the term "shape activity" has been used to denote a particular stochastic model for shape deformation. Dynamical models have been proposed for characterizing stationary shape activities (assume constant mean shape). In this work we define stochastic dynamic models for non-stationary shape activities and show that the stationary shape activity model follows as a special case of this. Most activities performed by a group of moving landmarks (here, objects) are not stationary and hence this more general model is needed. We also define a piecewise stationary model with non-stationary transitions which can be used to segment out and track a sequence of activities. Noisy observations coming from these models can be tracked using a particle filter. We discuss applications of our framework to abnormal activity detection, tracking and activity sequence segmentation.