Virtual observers in a mobile surveillance system

Abstract

Conventional wide-area video surveillance systems use a network of fixed cameras positioned close to locations of interest. We describe an alternative and flexible approach to wide area surveillance based on observation streams collected from mobile cameras mounted on buses. We allow a “virtual observer” to be placed anywhere within the space covered by the sensor network, and reconstruct the scene at these arbitrary points. Use of such imagery is challenging because mobile cameras have variable position and orientation, and sample a large spatial area but at low temporal resolution. Additionally, the views of any particular place are distributed across many different video streams. Addressing this problem, we present a system in which views from an arbitrary perspective can be constructed by indexing, organising, and transforming images collected from multiple streams acquired from a network of mobile cameras. Our system supports retrieval of raw images based on constraints of space, time, and geometry (eg. visibility of landmarks). It also allows the synthesis of wide-angle panoramic views in situations where the camera motion produces suitable sampling of the scene and metaphors for query and presentation that overcome the complexity of the data.