DARPA and the US Army have taken the wraps off ARGUS-IS, a 1.8-gigapixel video surveillance platform that can resolve details as small as six inches from an altitude of 20,000 feet (6km). ARGUS is by far the highest-resolution surveillance platform in the world, and probably the highest-resolution camera in the world, period.
ARGUS, which would be attached to some kind of unmanned UAV (such as the Predator) and flown at an altitude of around 20,000 feet, can observe an area of 25 square kilometers (10sqmi) at any one time. If ARGUS was hovering over New York City, it could observe half of Manhattan. Two ARGUS-equipped drones, and the US could keep an eye on the entirety of Manhattan, 24/7. Read more of this post