In 1970 the US did indeed have satellites photographing everything from space. I've seen low res samples of some. You can buy copies these days, if you want a black and white photo of some particular strip of the earth, maybe a km wide and several km long, from some date in 1970. I think the full resolution is something of the order of 1m features or even a bit less. Whether you would be able to tell if a sunbather was clothed or not, I can't say. You would probably be able to tell it was a person.
These were photos taken on big rolls of film which were later ejected in a capsule and fell back to earth, and I believe they were intended to be caught in mid air as they hung on a long line from a parachute. Quite extraordinary.
However amazing this was for the time, you have to keep it in perspective. They were not of course live photos. They could not be viewed until brought back, developed and printed. The satellites scanned strips of land one after another, whether there was anything interesting there or not. It's not James Bond: the CIA could not press a button and zoom in on the girls lying on the beach.