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Maritime Information

1. What is 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 an MMSI, how do I get one, and how do I program my AIS? A unique and official 9-digit Maritime Mobile Service Identity (MMSI) number is required for every AIS station. To obtain one see our MMSI page. While special attention should be taken in installing an AIS (see IMO Safety of Navigation Circular.227, GUIDELINES FOR THE INSTALLATION OF A SHIPBORNE AUTOMATIC IDENTIFICATION SYSTEM), its initial programming is relatively straightforward; please see our USCG AIS Encoding Guide for further instructions. Note, AIS information programmed into the unit (i.e. MMSI, call-sign, name, etc.) should reflect the vessel’s official data as provided in its radio station license or state registration (for those vessels licensed by rule).

After initial programming, users must ensure their AIS is always in effective operating condition and broadcasting accurately (33 CFR §164.46(b)). Failure to do so could subject a person to civil penalties not to exceed $25,000 (46 U.S.C. 70119). Note, each USCG type-approved AIS has an internal built-in integrity tester that mitigates the need to send TEST text messages. For further guidance on the programming and use of AIS text messages please read USCG Safety Alert 05-10.

3. What is the AIS rule and are there alternatives to the rule for small businesses? 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. 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. Note, 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? A USCG type-approved AIS can range in price between $500-$1,500 for AIS Class B and $3,000-$5,500 for AIS Class A devices; not including installation cost which will vary considerably depending on the level of integration of the AIS with other shipboard systems (e.g. gyro, rate of turn indicator, navigation positioning system, radar, charting systems, etc.). View a functional comparison of AIS Class A and Class B devices.

5. How does AIS help to increase security (and what is NAIS)? Although AIS is primarily and foremost a navigation tool for collision avoidance, the Coast Guard believes that the AIS will improve security also. AIS and 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? No, however, Chapter V, Regulation 19 of the Safety of Life at Sea Convention (SOLAS), as stated in 33 CFR § 164.46(a)(2), does require vessels on international voyage to interface it to other existing onboard equipment (i.e. transmitting heading device, gyro, rate of turn indicator); domestic vessels, are not currently required to do so, however it is highly recommended.

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 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. 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. Are fishing vessels subject to AIS carriage, and, are onboard Vessel Monitoring Systems (VMS) an acceptable substitute for AIS? Most fishing vessels are not currently subject to AIS carriage requirements, except for those on International voyage and of 300 gross tonnage (GT ITC) or greater (see 33 CFR 164.46(a)(2)). Note, the fishing vessel exception in 33 CFR 164.46(a)(1) and (a)(3)(i) only applies to fishing vessel' as defined in 46 USC 2101, which means a vessel that “commercially engages in the catching, taking, or harvesting of fish or an activity that can reasonably be expected to result in the catching, taking, or harvesting of fish”; it does not extend to domestic 'fish processing vessels' or 'fish tender vessels' transiting a Vessel Traffic Service area.

AIS and Vessel Monitoring Systems (VMS) are not inter-operable or compatible, each uses different communication systems, protocols, reporting rates, and, most importantly VMS does not mitigate collision or enhance situational awareness; therefore, VMS is not an acceptable substitute for AIS. 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 here, 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 should, 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. Here is a listing of Coast Guard type-approved AIS Class A units which require a firmware update in order to display AIS Class B information.

14. Do AIS Class B devices meet current USCG AIS carriage requirements? No. 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. See a comparison of Class A and Class B/CS AIS.

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 Notice of Proposed Rulemaking (73 FR 78295) to amend the current AIS regulations (68 FR 60559) and further harmonize the AIS mandates of Regulation V/19.2.4 of the Safety of Life at Sea Convention, and, the Maritime Transportation Security Act of 2002 (MTSA) by requiring AIS on most commercial vessels navigating U.S. navigable waters. For further information on this rule or to view the public submissions and all our supporting documents, visit [Search: USCG-2005-21869].

The USCG "Vessel Requirements for Notices of Arrival and Departure (NOAD) and Automatic Identification System (AIS) [USCG-2005-21869]" Final Rule regarding expansion of NOAD and AIS requirements in the U.S. completed its E.O. 12886 Regulatory Review at the White House Office of Information and Regulatory Affairs (OIRA) on December 24th, 2014; and, will be published in the Federal Register in January 2015.

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:

17. Where can I get AIS data? Although the U.S. Coast Guard operates our Nation's AIS network (NAIS), we do not --currently-- make our AIS information available to the general public. There are, however, numerous AIS networks and commercial purveyors that do provide AIS data and track information on the World Wide Web; many of which are listed on Wikipedia's AIS webpage. Local, state and federal government agencies may request U.S. Coast Guard Nation-wide AIS data here.

18. Reserved for future use.

19. What is AIS Channel Management? One of the lesser known and potent features of AIS is its ability to operate on multiple channels of the VHF-FM marine band. This frequency agility ensures AIS can be used even when the default channels are otherwise unavailable or compromised. In such conditions, competent authorities, such as the Coast Guard, can use an AIS base station to tele-command shipborne AIS devices to other more appropriate channels when within a defined region(s) of 200 to 2000 square nautical miles. This can be done automatically (and without user intervention) by receipt of the AIS channel management message (AIS message 22) or manually entered via the AIS Minimal Keyboard Display (MKD) or similar input device. Once commanded or inputted the channels management information will stay in memory for 5 weeks or until a vessel exceed 500 nautical miles from the defined region. AIS channel management commands can only be automatically overridden via another channel management message for the same defined region or manually overridden or erased by the user via the unit’s channel (regional frequencies) management function—read more. Note, reinitializing or resetting your AIS or transmission channels will not necessarily reprogram your unit back to default channels.

20. Can I use my AIS in an emergency or for distress messaging? Yes, but, be aware that AIS safety related text messages are not -currently- received, processed, recognized or acted upon as Global Maritime Distress Safety Systems (GMDSS) messages would be by the Coast Guard or other maritime first responders. Therefore, AIS should not be relied upon as the primary means for broadcasting distress or urgent communications, nor used in lieu of GMDSS such as Digital Selective Calling radios which are designed to process distress messaging. Nonetheless, AIS remains an effective means to augment GMDSS and provides the added benefit of being 'seen' (on radar or chart displays), in addition to being 'heard' (via text messaging) by other AIS users within VHF radio range. For further guidance, see USCG Safety Alert 5-10. Also see, International Maritime Organization’s (COMSAR) Circular 46, USE OF AIS SAFETY-RELATED MESSAGING IN DISTRESS SITUATIONS.

21. Is the Coast Guard broadcasting AIS Aids to Navigation Reports? Yes. The U.S. Coast Guard and other authorized agencies and organizations (i.e., U.S. Army Corps of Engineers, National Oceanic and Atmospheric Administration, Marine Exchange of Alaska) are or will begin transmitting AIS ATON Report and marine safety information via AIS (see our Special Notice 01-2014).  The exact content, location, and times of these transmissions will be announced in the Coast Guard Local Notices to Mariners (LNM). For further information on AIS ATON refer to the various IALA Guidelines and Recommendations.

22. Have an AIS question not answered here? Please contact us.