1. A method comprising: displaying a first image corresponding to a field of view of at least one camera, providing a user interface that allows a user to: identify a first region of the first image at which objects may disappear from the image, identify a second region of a second image at which objects may appear in the other image, and define a first likelihood that an object that disappears from the first region will appear in the second region, and subsequently identifying a target object in the first image, and determining whether the target object appears in the second image based on the first likelihood and an object similarity measure.