stands for Interface Control Document for GPS User Equipment (Non-Standard) for the Precise (P/Y) Code . While the number "153" is less famous than its civilian counterpart (ICD-GPS-200), it is arguably more critical for national security.

NMEA 0183 "talkers" can be, for example, a satellite, a depth sounder, or a compass, while the "listeners" can be a chart-plotter, Arduino Docs Ruggedized, Tactical GPS Time and Frequency System

Write a state machine to parse the binary sync words. Do not search for ASCII strings (like $GPGGA ). Use a circular buffer and check CRC before processing.

Without ICD-GPS-153, a military computer cannot decrypt the secure P(Y) code. The protocol manages the and zeroization (securely erasing classified keys) that are mandatory for SAASM compliance.