Because the protocol is often associated with military-grade GPS equipment, the full technical document is not always available for direct public download.
Devices like the Safran NetClock use ICD-GPS-153 messages to provide 1PPS (pulse-per-second) and time-of-day information to external equipment without requiring a full military-grade receiver for simple time-only tasks. icd-gps-153 protocol
Also sent at 1 Hz, this message is essential for high-accuracy time synchronization between the GPS and the connected system. Because the protocol is often associated with military-grade