Did a tour around my place a year or so ago, with a atate of the art GPS unit, hoping to figure out my actual acreage (those old land grants are just so vague);
by the time I got back around to where I started, the GPS showed I was 67 feet away.
They're going to REALLY have to fine tune that system before it could ever control vehicle movements.
"atate" = state
Arrrrgh!