Thanks for the answer Seldom Seen. Ax25 and AFSK make perfect sense. BTW-the message sent from the GPS to the TNC is a NMEA-0183 GGA message. This is the autonomous location of the GPS receiver and should be accurate to about 6-10 meters CEP. There are many other message types that could be used including velocity and timing.
You can read about NMEA here: http://www.nmea.org/pub/0183/
and Here: http://www.nmea.org/pub/0183/
03 UZJ100 (2.5" OME/Slee suspension), LEDs, cross drilled and slotted rotors by PowerStop, and some other goodies.
75 FJ40 with stuff; and now weighing in at 4370 lbs.