Surveillance drones to be used for first time at Boston Marathon

Stepping up security measures, authorities will use surveillance drones, equipped with zoom lenses and infrared at this year's Boston Marathon. More than 30,000 runners are expected to attend, and around a million spectators.

The two drones will fly 400 feet above the starting line, tethered by thin wire, where long-distance lenses, electro-optical and infrared cameras will send video feed to police command centers.  Read more.