Mostly Trimble Navigation Ltd. gear. They're built like tanks and well past IP67 because they're also used in mines on enormous equipment.
Disclaimer: I used to work on the TRIMMARK and TRIMCOMM series firmware in the radio group. With kinematic (moving differential-capable) corrections plus a fixed base station, horizontal accuracy is sub cm (10 mm) and vertical is sub meter. Two receivers, one on either side of the vehicle, can be used to accurately guide the side-to-side angle of plowing, grading, or other activities.
