ICD-GPS-153 defines the serial communication protocol (RS-232/RS-422) for U.S. Department of Defense GPS User Equipment. It establishes standardized messages for high-accuracy timing and position data, supporting military-grade receivers with SAASM security. Authorized users can request the full specification through the U.S. Coast Guard Navigation Center. GSSIP Message Format - Safran - Navigation & Timing
ICD-GPS-153 is the formal Interface Control Document (ICD) that defines the GPS Standard Serial Interface Protocol (GSSIP). It is primarily used to control the input and output of data between military GPS receivers—such as the Defense Advanced GPS Receiver (DAGR) and the Precision Lightweight GPS Receiver (PLGR)—and other systems, typically military aircraft and vehicles. Purpose and Scope
Tactical Data Exchange: It facilitates data messaging capabilities between receivers and host platforms.
Military Standard: Unlike the civilian NMEA-0183 protocol, which uses text-based ASCII messages, ICD-GPS-153 is a more robust protocol designed for military and government data streams.
Secure Operations: It supports communication for Selective Availability Anti-Spoofing Module (SAASM) receivers, providing protection against jamming and spoofing. Technical Characteristics
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In the high-stakes world of defense and precision navigation, communication is everything. This is the story of ICD-GPS-153
, the invisible "translator" that ensures elite GPS receivers and military hardware speak the same language. The Problem: A Digital Tower of Babel Imagine a military humvee equipped with a high-precision Defense Advanced GPS Receiver (DAGR)
. On its own, the DAGR knows exactly where it is. However, the vehicle’s onboard tactical computer—which maps the terrain and coordinates with other units—needs that data instantly and accurately.
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)
Think of it as a strict set of grammar rules for RS-232 and RS-422 serial connections. It defines exactly how a GPS receiver should "package" its data—latitude, longitude, altitude, and time—so that any compliant system can read it instantly. How It Works in the Field The Request
: A tactical mission computer sends a "query" packet using the ICD-GPS-153 format. The Response : The GPS receiver (like a PLGR or DAGR
) identifies the request and replies with a standardized data burst. The Result
: Because both devices follow the same Interface Control Document (ICD), there is no "lost in translation." The vehicle's map updates in real-time, allowing for precise navigation through contested environments. Why It Matters Interoperability : You can swap out an old receiver for a modern SAASM-enabled one without rewriting the vehicle's entire software.
: By standardizing the interface, engineers can better protect the data flow against interference or "spoofing" attempts. Reliability icd-gps-153 protocol
: In critical missions, there is no room for "signal not found." ICD-GPS-153 provides the rock-solid reliability required for military land, sea, and air operations
Today, while newer protocols exist, ICD-GPS-153 remains a cornerstone of legacy and modern Military GPS systems
, ensuring that no matter the hardware, the mission stays on course. technical breakdown
of the specific message types or packet structures used in this protocol? NAVAL POSTGRADUATE SCHOOL THESIS - DTIC
ICD-GPS-153 is a specialized serial communication protocol used primarily for interfacing with military-grade GPS receivers, such as (Selective Availability Anti-Spoofing Module) units. Mayflower Communications Key Features Host Control
: It allows a host computer or navigation system to control the GPS receiver and request specific data outputs like Position, Velocity, and Time (PVT). Secure Data Exchange
: It is designed to work with military security architectures, supporting the exchange of encrypted and protected navigation data. Dual Frequency Support : The protocol handles data from both carrier frequencies, including C/A, P, and encrypted P(Y) codes Physical Interface : Typically implemented over (RS-232) serial connections. Standardized Integration
: It provides a standard messaging format so that different military GPS hardware (like the NavGuard 100
) can be swapped or integrated into various platforms like missiles, aircraft, or handheld devices. Mayflower Communications message formats or how it differs from commercial protocols like NavGuard® 100 SAASM GPS Receiver with Anti-Jam
The ICD-GPS-153 protocol is a standard serial interface used primarily by United States military GPS receivers, such as the DAGR (Defense Advanced GPS Receiver) and PLGR (Precision Lightweight GPS Receiver). Unlike the common civilian NMEA-0183 protocol, it is designed to handle encrypted and secure data, including time and frequency synchronization for tactical systems. Core Functionality
Secure Interface: Provides a standardized way for host platforms (vehicles, aircraft, handhelds) to communicate with SAASM (Selective Availability Anti-Spoofing Module) receivers.
GSSIP Support: Often referred to as the GPS Standard Serial Interface Protocol (GSSIP).
Synchronization: Frequently used to provide precision time transfer (1PPS) and frequency control to networked systems. Common Message Types
While the full specification is restricted to authorized personnel, standard implementations include these key periodic updates: Message Type Current Status Real-time health and status of the GPS receiver. Time Transfer Precise time of day (UTC) and Leap Second information. Buffer Box Once every 6s Security
Extended data used for legacy system emulation (e.g., SINCGARS). Key Comparisons
GPS NMEA 0183 Messaging Protocol 101 - Arduino Documentation
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
Understanding the ICD-GPS-153 Protocol: The Backbone of Military GPS Integration
The ICD-GPS-153 (Interface Control Document for the RS-232/RS-422 Interface of DoD Standard GPS User Equipment) is a critical technical standard that defines how military Global Positioning System (GPS) receivers communicate with host platforms. Unlike the consumer-grade NMEA 0183 protocol common in civilian devices, ICD-GPS-153 is designed for the rigorous demands of Department of Defense (DoD) hardware. What is ICD-GPS-153?
At its core, ICD-GPS-153 is a binary communication protocol used to transfer functional data between a GPS receiver and a host system, such as a vehicle’s navigation computer or a handheld tactical device. It establishes the rules for the RS-232 and RS-422 serial interfaces found on standard military GPS User Equipment (UE).
While consumer protocols often focus solely on providing location coordinates, ICD-GPS-153 is built to handle complex tasks required in high-stakes environments:
Time Transfer: Synchronizing tactical networks with nanosecond precision.
Status Reporting: Providing detailed "Figure of Merit" (FOM) data to indicate the reliability and validity of position and velocity fixes.
Cryptographic Support: Interfacing with Selective Availability Anti-Spoofing Modules (SAASM) and M-Code ready receivers for secure, encrypted signaling. Key Message Types and Formats
The protocol is organized into specific message formats that support various operational modes. For instance, the ICD-GPS-153C revision is frequently cited in systems that emulate SINCGARS (Single Channel Ground and Airborne Radio System) interfaces. Commonly used messages include:
Current Status (Message 5040): Transmitted at 1Hz to provide real-time operational health.
Time Transfer (Message 5101): Transmitted at 1Hz to deliver precise UTC time and 1PPS (pulse per second) alignment.
Buffer Box (Message 253): Sent every 6 seconds to support specific interface emulation. Applications in Military Hardware Authentication:
You will primarily find ICD-GPS-153 implemented in ruggedized tactical systems. It is the standard interface for iconic military GPS receivers like the PLGR (Precision Lightweight GPS Receiver) and the DAGR (Defense Advanced GPS Receiver). Modern applications include:
Time and Frequency Systems: Tactical clocks use this protocol to provide stable timing to networks even in GPS-denied environments.
Land Navigation: Military vehicle GPS units, such as those from SITEP Italia, utilize the protocol to integrate with on-board computers.
Secure Communication: It facilitates the loading of "Black Keys" and handles Over-The-Air-Rekeying (OTAR) for secure satellite communication. Accessing the Full Specification
Due to its sensitive nature, the full technical manual for ICD-GPS-153 is not always available for public download. While some versions can be found through military technical libraries, the U.S. Coast Guard Navigation Center typically requires a signed GPS Technical Library Document Request form for the most current, non-public releases.
ICD-GPS-153 receivers operate in two primary modes:
Sometimes, non-standard ICD numbers (like a hypothetical 153) refer to Control Segment documents (how the Air Force controls the satellites) rather than the User Segment (how users receive signals).
The most complex aspect of ICD-GPS-153 is its integration with military GPS security. Standard ICD-GPS-153 messages are not inherently encrypted—the protocol defines the container. However, the payloads for precision data (Type 1, 2, 26) can be encrypted using the GPS security architecture.
When a host system sends a command to the receiver, the receiver uses its internal SAASM or M-Code module to decrypt the GPS signals. The results are then repackaged into ICD-GPS-153 messages. The host never sees the raw classified keys.
Critical Security Commands in ICD-GPS-153:
To understand the importance of ICD-GPS-153, one must grasp the fundamental difference between civil and military GPS signals.
| Feature | Civil GPS (L1 C/A) | Military GPS (ICD-GPS-153) | | :--- | :--- | :--- | | Signal | 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. |
Without ICD-GPS-153, a military computer cannot decrypt the secure P(Y) code. The protocol manages the session key negotiation and zeroization (securely erasing classified keys) that are mandatory for SAASM compliance.