Estimation of multiple 2-D uniform motions by SLIDE: subspace-based line detection

A technique is proposed for estimating the parameters of two-dimensional (2-D) uniform motion of multiple moving objects in a scene, based on long-sequence image processing and the application of a multiline fitting algorithm. Plots of the vertical and horizontal projections versus frame number give new images in which uniformly moving objects are represented by skewed band regions, with the angles of the skew from the vertical being a measure of the velocities of the moving objects. For example, vertical bands will correspond to objects with zero velocity. An algorithm called subspace-based line detection (SLIDE) can be used to efficiently determine the skew angles. SLIDE exploits the temporal coherence between the contributions of each of the moving patterns in the frame projections to enhance and distinguish a signal subspace that is defined by the desired motion parameters. A similar procedure can be used to determine the vertical velocities. Some further steps must then be taken to properly associate the horizontal and vertical velocities.