The science is based on pattern recognition technology and statistics, in two stages. First, is the training phase in which the system becomes familiar with the behaviour observed by the camera network. Once achieved, the second stage is to track a particular person’s movement over time. Dr Orwell points out that they can’t use face recognition because the images are too small: ‘we generally try to use the colour and composition of their clothing. So you form a representation of what they look like and you look for that in other images from other cameras.’
The system is designed to work in a real time mode, monitoring places where the system expects to see a person; and a forensic mode where previous footage can be examined for evidence.
There are plans to include an alarm bell mode. Dr Orwell gives the example in an airport of a person walking through a door the wrong way, or trespass in a secure area. He explains, ‘the system would then be used in a forensic capability. What we are able to provide is much faster in terms of locating the relevant images and a clearer image of that person.’