Harold27Z said:

How else could precision crop-circles be produced ?

By VERY clever people.

Di (amina046) said:

As usual  you are way off the content.

Indeed, 

And we know exactly how crop-circles were made.

Jenifer (Zarknorph) said:

GPS is everywhere - on your phone, in your car, even on your wrist. But it hasn't always been as ubiquitous as it is today.

I didn't realise it was implemented first in 1991, the Gulf War (that we insultingly call "1" when its very much "2").

Austrian actress Hedy Lamarr, together with a friend whose name I forget,  was the person who started the invention of blue-tooth and gps.