A Boeing A160 Hummingbird drone. This rotor-based aircraft is capable of vertical take-offs and landings. The craft is affixed with the DARPA-developed ARGUS-IS imaging system -- which boasts a 1.8 gigapixel camera that can "track people and vehicles from altitudes above 20,000 feet."
This Massive Camera Will Capture the Entire Southern Sky | The Large Synoptic Sky Survey will find countless objects and phenomena, near and far, never seen before. [Future Space Technologies: http://futuristicnews.com/category/future-space/]
From an altitude of 20,000 ft, DARPA's newest aerial surveillance camera, ARGUS-IS, can keep a real-time video eye on an area 4.5 miles (7.2 km) across down to a resolution of about six inches (15 cm).