While the exact mathematical details are classified, the unclassified architecture of ICD-GPS-153 is well-understood.
Without a standard protocol, every GPS manufacturer would use their own "language." The tactical computer would need a different driver for every device, leading to delays, errors, and system failures in the field. The Solution: The Universal Handshake To solve this, the U.S. Department of Defense established ICD-GPS-153 , officially known as the GPS Standard Serial Interface Protocol (GSSIP) icd-gps-153 protocol
The most probable target of your inquiry is (officially titled Navstar GPS Space Segment/Navigation User Interfaces ). While the exact mathematical details are classified, the