The techniques of aerial photo analysis and interpretation had been really well developed during World War II. There's an awful lot you can learn from shadows, for instance, or looking not just at buildings but at the parking area, trucks or railcars adjacent, stacks of materials, etc. During the 1950s, color and particularly color infrared film allowed photointerpreters to know much more about crops, road usage, even the activities inside buildings. So very little about the imagery coming from satellites was new—just lower resolution and sometimes compromised by clouds and atmospheric interference.