How does facial recognition technology work?published at 16:16 British Summer Time
16:16 BST
Thomas Copeland
BBC Verify Live journalist
Image source, Getty Images
We’ve been talking today about facial recognition technology and how it is used. But how do these tools actually recognise your face?
Prof Pete Fussey is an expert in advanced surveillance at the University of Southampton.
He says the process used by Live Facial Recognition (LFR) vans can be roughly simplified into three steps.First, police decide who they want to target and compile a database of individuals fitting that profile.
“That profile could be based on a type of offence, a court order or just people the police want to talk to,” says Fussey. This watch list will include photographs, usually taken from custody records.
Second, the images from the database and the live images filmed by the van’s cameras are converted into a code based on biometric information about the person’s face. This is the same technology used by Face ID on an Apple iPhone.
“It measures parts of your face that don’t change over time, like the distance between your eyes, and also the relationships between your features, like the size of your eyes compared with your mouth,” explains Fussey.
Finally, the police will set a similarity threshold between 0 and 1. In most cases, a similarity score of about 0.6 will be flagged to the person operating the system as a potential match. The higher the score the greater the confidence that the system has correctly made a match.