Probably nowadays they use a lot of GPS mapping to get the patterns?
In 20 years, crop circle making will look so trivial people will say, why would the aliens bother.
Anyway, my personal take on aliens/ abductions/ etc. is that aliens may not even need to visit us. All they need to have are subspace transmission capabilities and they could be communicating directly with our minds. Forget all the debate on "oh it's too far away", or "they want to test us" and all that nonsense. In just 2,000 years we could easily remotely scan and communicate with life forms within a 10,000 light year range.
Given the age of the universe, multiple dimensions and so on, the truth *is* really out there.
And we haven't even cracked harnessing subatomic particles, smashing particles together is the equivalent of apes bashing rocks together trying to make a useful tool. But unlike millions of years (supposedly), it's just within a few hundred years that we are able to sensibly (assuming we don't annihilate ourselves) harness this technology.
Again this is all conjecture on just what we know, I mean, just 100 years ago would people have expected that a little box in the sky can show our house from space, right in the palm of our hands.....?
The door is wide open now, peoples, the mind [note: not "brain"] is the final frontier.