Building a Stratum 1 NTP server with GPS Time Reference
ETH Zürich has a write-up about building an inexpensive embedded Stratum 1 time server using a PC Engines ALIX board and a Garmin GPS 18x OEM (aprx $50) which supports the highly accurate one-pulse-per-second (PPS) output.
- The LinuxPPS Project – An implementation of the Pulse Per Second (PPS) API for GNU/Linux version 2.6
- Adding a FreeBSD NTP server based on an GPS 18 LVC device
- Wolfgang S. Rupprecht’s GPS Hacks