...
GPS
Actually GPS coupled with an onboard computer that steers the tractor.
...and in some cases the additional aid of a drone running ahead of the tractor to scope out obstacles (rocks, washouts, etc).
BIL has one that has more electronics than I can recall seeing on front-line Navy aircraft back in The Day.....I've teased him about sending the tractor out to plow while he's back in the kitchen drinkin' coffee.
And the so-and-so just grinned at me.
Using GPS on a tractor in order to draw sounds very complicated. I’m glad this farmer warmed POTUS’ heart.
He must be at least as thirsty for justice as we are!
Thank you for your answers!