[myself248]

Yeah but you don't need commercial services to get down to the inch anymore. Running your own base station has gotten cheap and easy; witness Sparkfun selling their RTK Express kit like hotcakes.

Integrating it into the vehicle is a fun second ROS project for someone who already built a toy robot car. There's a substantial population of highschoolers building the necessary skills, the trick is just to connect them to the jobs.