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Automatic ID System (AIS)
Primary Mission Areas:
Maritime Information:
FREQUENTLY ASKED QUESTIONS

1. What is the AIS? Per 47 CFR §80.5 AIS is a maritime navigation safety communications system standardized by the International Telecommunication Union (ITU) and adopted by the International Maritime Organization (IMO) that provides vessel information, including the vessel's identity, type, position, course, speed, navigational status and other safety-related information automatically to appropriately equipped shore stations, other ships, and aircraft; receives automatically such information from similarly fitted ships; monitors and tracks ships; and exchanges data with shore-based facilities. Read more on what it is, how it works, what it broadcasts, and, the messages it uses, etc.

2. What is the AIS rule? The U.S. Coast Guard has developed rules applicable to both U.S. and foreign-flag vessels that require owners and operators of most commercial vessels to install and use the AIS. The AIS rule is part of our domestic and international effort to increase the security and safety of maritime transportation. See 33 CFR parts 26, 161, 164, and 165. Current AIS regulations, 33 CFR §164.46, became effective on November 21, 2003, and, require that all vessels denoted 33 CFR § 164.46(a) be outfitted with an USCG 'type-approved' and 'properly installed' AIS no later than December 31, 2004. Read more.

3. Are there alternatives to the AIS rule for small businesses? No, there are no special provisions or alternatives in the AIS rules for small businesses. See Small Entity Compliance Guide to AIS.

4. How much does an AIS cost? An USCG type-approved AIS can range in price between $600 (AIS Class B) and $5000 (AIS Class A), not including installation cost which will vary considerably depending on the level of integration of the AIS with other shipboard systems (e.g. radar, speed log, rate of turn indicator, navigation positioning system, ECDIS, etc.).

5. How does AIS help to increase security? Although AIS is primarily and foremost a navigation tool for collision avoidance, the Coast Guard believes that the AIS will improve security also. AIS ad our Nationwide AIS Project (NAIS) increases the Coast Guard’s awareness of vessels in the maritime domain, especially vessels approaching U.S. ports. The AIS corroborates and provides identification and position of vessels not always possible through voice radio communication or radar alone.

6. When must AIS be in operation? Vessels equipped with AIS (either by mandatory carriage or voluntarily) must abide by the requirements set forth in Title 33, Code of Federal Regulations, §§ 164.46 and 161.20, and should especially ensure their AIS is in 'effective operating condition’, which entails the continuous operation of AIS and the accurate input and upkeep of AIS data fields during all times that the vessel is navigating (underway or at anchor). Should continual operation of AIS compromise the safety or security of the vessel or where a security incident is imminent, the AIS may be switched off. This action and the reason for taking it must be reported to the nearest U.S. Captain of the Port or Vessel Traffic Center and recorded in the ship's logbook. The AIS should return to continuous operation as soon as the source of danger has been mitigated.

7. Does the installation of the AIS require additional equipment in order for the AIS to operate properly? Maybe. Most AIS do not need additional equipment (sensors) in order to operate; a few however, do require interfacing with an external global navigation positioning device (e.g. dGPS, GPS, GLONASS) in order to accurately calculate and broadcast position, course, and speed--thus requiring this equipment to properly operate. Although not required for the operation of AIS, Chapter V, Regulation 19 of the Safety of Life at Sea Convention (SOLAS), as stated in 33 CFR § 164.46(a)(2), does require certain vessels--those on international voyage--to also interface other onboard equipment (i.e. transmitting heading device, gyro, rate of turn indicator) to the AIS; domestic vessels, not on international voyage, are not currently required to do so, however are highly recommended to.

8. Will it be necessary to have electronic navigational charts for use with the AIS? Eventually. Section 410 of the Coast Guard and Marine Transportation Act of 2004 (P.L. 108-293) directs the Coast Guard to prescribe regulations that will require most commercial vessels "while operating on the navigable waters of the United States...be equipped with and operate an electronic chart system (ECS)"; and, that this system be integrated with AIS. A rulemaking implementing this additional requirement is in development and is expected to be published later this year (2006). Till these regulations are finalized, AIS is not required to be displayed on an ECS or other external display system; although it is highly recommended. The full benefits of AIS are only achieved when it is fully integrated and displayed on other shipboard navigation systems (e.g. Electronic Charts Data & Information System (ECDIS), ECS, Radar, Automatic Radar Plotting Aide (ARPA), Tracking Devices, personal software, etc.).

9. If a fishing vessel has a Vessel Monitoring System (VMS) that provides vessel identification and location data, is the VMS an acceptable substitute for the AIS? No, it is not. The AIS and VMS are not inter-operable, each uses different communication systems, protocols, and, reporting rates that make them incompatible. Read more...

10. Why have some AIS units stopped broadcasting valid position reports? On February 27th, 2008 the GPS constellation increased to 32 satellites (PRN 32) thus providing a 5% increase in satellite availability and DOP (dilution of precision) world-wide. It has come to our attention that some (non-USCG type approved) AIS units—particularly old equipment which is non-compliant with the GPS interface standard (IS-GPS-200)—cannot recognize this additional satellite and subsequently are unable to calculate a position and broadcast a valid AIS Position Report. Note, the reported malfunctioning units do continue to receive position reports and are able to send and receive AIS text messages. Owners of AIS equipment denoted at http://www.navcen.uscg.gov/lnm/Saab_R3_AIS_prob.htm, however, should be aware that their internal GPS systems may not act as a proper—timing or position—back-up under certain circumstances, i.e. when in view of PRN32. AIS users must ensure their units have or are interfaced with a properly operating Electronic Position Fixing System at all times. GPS and/or AIS problems should be reported via the NAVCEN website or via phone to the USCG Navigation Information Service at 1-703.313.5900.

11. Why am I unable to see an AIS vessels' name or other static information (dimensions, call sign, etc.)? Shipboard AIS units autonomously broadcast two different AIS messages: a 'position report' which includes the vessels dynamic data (e.g. latitude, longitude, position accuracy, time, course, speed, navigation status); and, a 'static and voyage related report' which includes data particular to the vessel (e.g. name, dimensions, type) and regarding its voyage (e.g. static draft, destination, and ETA). Position reports are broadcasted very frequently (between 2-10 seconds-depending on the vessels speed-or every 3 minutes if at anchor), while static and voyage related reports are sent every six minutes; thus it is common and likely that an AIS user will receive numerous position reports from a vessel prior to receipt of the vessels' name and type, etc.

12. Why do I sometimes see more than one vessel with the same MMSI or vessel name (i.e. NAUT)? AIS users are required to operate their unit with a valid MMSI, unfortunately, some users neglect to do so (for example, use: 111111111, 123456789, 00000001, their U.S. documentation number, etc). A valid MMSI will start with a digit from 2 to 7, a U.S. assigned MMSI will start with either 338, 366, 367, 368, or 369. AIS users whom encounter a vessel using MMSI: 1193046 or named: NAUT should notify the user that their AIS unit is broadcasting improper data; see Nauticast AIS-MMSI Technical Bulletin for further information. All AIS users should check the accuracy of their AIS data prior to each voyage, and, particularly units that have been shutdown for any period of time. NOTE: If you are receiving (in range of) AIS reports from vessels using the same MMSI, they will appear as one vessel (jumping from position-to-position or line-to-line) on a graphical screen (e.g. ECS, ECDIS, radar) or on the AIS Minimal Keyboard Device (MKD).

13. I just purchased and installed an AIS Class B, will AIS Class A users ‘see’ me? Most , but, soon all will. Although all Class A devices will receive Class B information; unfortunately, some older Class A models are unable to display this information on their Minimum Keyboard and Display (MKD) or may only have available the Class B vessel’s dynamic data (i.e. position, course and speed) but not its static data (i.e. vessel name, call-sign). Therefore, the Coast Guard cautions new AIS Class B users to not assume that they are being ‘seen’ by all other AIS users or that all their information is available to all Class A users. Further, we exhort users of certain AIS Class A units to, as soon as practicable, update their MKD’s and/or other external navigation display systems (e.g. Electronic Charts Systems, Electronic Chart & Display Information Systems, radar, etc.) in order to view this new stream of valuable AIS information that will enhance navigation safety and mitigate the risk of collision. A rulemaking to mandate such an update is forthcoming. For a listing of Coast Guard type-approved AIS Class A units which require a firmware update in order to display AIS Class B information, click here.

14. Do AIS Class B devices meet current USCG AIS carriage requirements? Although the Coast Guard encourages the wide use of AIS, we advise mandated AIS users that Class B devices do not meet current International Convention for the Safety of Life at Sea (SOLAS V/19.2.4) or U.S. domestic AIS carriage requirements (33 CFR 164.46). The Coast Guard is in the process of expanding the current carriage requirements (to most self-propelled commercial vessels which navigate U.S. waters) and Class B devices will be permissible on some commercial vessels, however, not for all of them. Thus, we take this opportunity to inform prospective buyers, particularly commercial vessels that are highly maneuverable, travel at high speed, or routinely transit congested waters or in close-quarter situations with other AIS equipped vessels, that AIS Class A devices, albeit more expensive, are a better option and will meet any future requirements we may impose.

15. Is the USCG considering expanding AIS carriage to other vessels or outside of VTS areas? Yes. On December 16th, 2008 the Coast Guard published a proposed rule to amend the current AIS regulations, and, expand AIS requirements—beyond Vessel Traffic Service (VTS) areas to all U.S. navigable waters and require AIS carriage for additional commercial vessels, including commercial vessels carrying 50 or more passengers, fishing vessels 65 feet or greater, hi-speed passenger vessels, dredges and floating plants operating in or near channels or fairways, and vessels carrying or moving certain dangerous cargo. We invite you to visit www.regulations.gov to view the public comments submitted on our proposal and to register for email notifications regarding future actions on this rulemaking.

16. How can I get a copy of an AIS presentation I saw (or heard about it) that was given at...You can download recent presentations given by Coast Guard Office of Navigation Systems personnel here:

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