The GPS-based NTP server started out as a project to synchronise the time on all the machines connected to the CS-Subnet. To do this we wrote a C Program that reads the time tag from the eTrex GPS that our CS department owns. The eTrex gets time from Satellites and outputs it in Navy Time Format. This output cna be read through a Serial Port on the GPS.

The current version of our time-reading program is "gettime.c" originally written by Charlie Peck, and Lew Riley, and modified by Chip Yeakey to read the $GPGLL tag from the GPS. This tag contains the required time information. We are running our program as a script from a machine called "Proto". The script takes the time read by gettime.c and updates Proto's Hardware and Software Clock to this new time. All the other machined on the CS-Subnet take the updated time from Proto.