In practice, receivers compliant with the protocol often use RS-232 serial communication for time-of-day data, alongside differential serial lines that can be configured as RS422 or RS485 for more robust communication. For example, a typical device might use RS-232 for NMEA 0183 and ICD-GPS-153 time-of-day data, while using RS422 for other protocols like HaveQuick.
The ICD-GPS-153 protocol was first introduced by the US Department of Defense (DoD) in the 1990s as part of the GPS (Global Positioning System) modernization effort. The protocol was designed to provide a standardized interface for GPS receivers to communicate with host devices, allowing for the exchange of GPS data, configuration, and control information.
| Feature | Civil GPS (L1 C/A) | Military GPS (ICD-GPS-153) | | :--- | :--- | :--- | | | L1 C/A (Unencrypted) | L1/L2 P(Y) code, M-Code (Encrypted) | | Accuracy | ~3-5 meters (with WAAS) | <1 meter (Precision Positioning Service) | | Security | None (vulnerable to spoofing) | Cryptographically authenticated (SAASM/M-Code) | | Protocol | NMEA 0183, UBX, RTCM | ICD-GPS-153 (binary, secure) | | Data Fields | Lat/Lon, Time, Speed, Course | Full PVT, plus velocity, acceleration, integrity, UTC, GPS time, and classified vectors. |
Often encapsulated within the framework, ICD-GPS-153 defines the syntax and timing of three critical ASCII messages: icd-gps-153 protocol
While commercial systems often use NMEA-0183, military applications require tighter security, more robust timing, and specialized status information. ICD-GPS-153 addresses this by providing high-precision data essential for tactical operations, such as:
, making it more efficient for high-speed data transmission in ruggedized or tactical environments. Device Compatibility
GLI-FLO is a secure GPS PNT distribution device approved by the U.S. Air Force GPS Directorate and fully ICD-GPS-153 compliant. One device can replace up to four DAGR receivers, distributing secure PNT data simultaneously to multiple weapon or communication systems. In practice, receivers compliant with the protocol often
The ICD-GPS-153 protocol, also known as the Interface Control Document for GPS 153, is a technical standard for communication between GPS devices and external equipment. The protocol defines the requirements for data exchange between GPS receivers and devices such as computers, autopilots, and other navigation systems.
The , also known as the GPS Standard Serial Interface Protocol (GSSIP) , is a critical technical specification governing how GPS receivers—specifically those with secure military capabilities—communicate with other defense systems. As an Interface Control Document (ICD), it defines the precise data structures, message formats, and timing required for interoperability between GPS hardware and tactical equipment.
ICD-GPS-153 is not publicly available on the GPS.gov public documents page due to its military nature. To obtain the full specification, users must typically follow a formal request process: The protocol was designed to provide a standardized
while (serial_available()) byte = read_byte(); if (byte == SYNC1 && next_byte() == SYNC2) msg_type = read_byte(); length = read_word(); payload = read_bytes(length); crc = read_word(); if (crc == calculate_crc(payload, length)) process_message(msg_type, payload);
The ICD-GPS-153 protocol is not an abstract technical specification—it is actively deployed in cutting-edge military and timing equipment. Here are several key examples:
It is also possible the number "153" was a corruption of .
: It provides a reliable pathway to handle cryptographic keys, over-the-air rekeying (OTAR) variables, and security status updates without leaking classified properties to unauthorized sub-systems.