I first heard about this on Radiolab. Maybe you heard it there too?
>> In 2004, when casualties in Iraq were rising due to roadside bombs, Ross McNutt and his team came up with an idea. With a small plane and a 44 mega-pixel camera, they figured out how to watch an entire city all at once, all day long. Whenever a bomb detonated, they could zoom onto that spot and then, because this eye in the sky had been there all along, they could scroll back in time and see - literally see - who planted it.