- Real Time Kinematics - RTK - is computation done upon regular GPS signals to determine location to within 5 cm by solving the integer ambiguity problem of carrier GPS wavelengths 
- Beagle Bone Blue for specialized rovers 
- 1 cm accuracy for under $300 
- Rover accuracy discussion - few centimeters! 
- GNSS modules cost $30 and are 2 meters accurate https://junipersys.com/support/article/6614].