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.

It is the definition of observe in this case that will blow your mind, though. With an imaging unit that totals 1.8 billion pixels, ARGUS captures video (12 fps) that is detailed enough to pick out birds flying through the sky, or a lost toddler wandering around. These 1.8 gigapixels are provided via 368 smaller sensors, which DARPA/BAE says are just 5-megapixel smartphone camera sensors. These 368 sensors are focused on the ground via four image-stabilized telescopic lenses.
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According to the Lawrence Livermore National Laboratory (LLNL), the processing of all that image data, 1.8 billion pixels at 12 fps, generates on the order of 600 gigabits per second. This equates to around 6 petabytes - or 6,000 terabytes - of video data per day. - ExtremeTech