Active contours or snakes are widely used for segmentation and tracking. Multiple object tracking remains a difficult task, characterised by a trade off between increasing the capturing range of edges of the object of interest, and decreasing the capturing range of other edges. We propose a new external force field which is calculated for every object independently. This new force field uses prior knowledge about the intensity of the object of interest. Using this extra information, this new force field helps in discriminating between edges of interest and other objects. For this new force field, the expected intensity of an object must be estimated. We propose a technique which calculates this estimation out of the image
