There is a printed circuit board (actually there are two) that determine instantaneous position data of the BuckBoty.  Each PCB has a GPS unit with antenna, a digital magneto-restrictive compass chip, 3 orthogonal accelerometers, and a pic24F08 microcontroller communicating with them over the I2C bus, and to the boss hawg controller over a shared serial bus (RS-422).  For further details (and download the schematic and Gerbers) you can go to:       http://www.ranarchy.org/DESIGN.html