The scanning system is known as Biometric Optical Surveillance System, or BOSS. It uses a computer to build a “3-D signature” from photos taken at different angles, then compares the results with a watch-list database. A computer professor and an official with the company developing BOSS said advances in computer processing will eventually result in speedier and more reliable matches. Currently, the system’s accuracy is only 60 percent to 70 percent at longer distances. And it takes 30 seconds to process the images.