The automatic identification system (AIS) is an automatic tracking system that uses transponders on ships and is used by vessel traffic services (VTS). Originally designed as a terrestrial communication system (ship to ship; ship to shore), satellites are now also used to passively capture the signal traffic. With a few exceptions, AIS traffic is in the form of continual status announcements of a sender to all interested parties in its proximity. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport, since AIS relies on the accuracy of information transmitted by other vessels, whereas radar independently detects objects. Although technically and operationally distinct, AIS is analogous to the ADS-B system which performs a similar function for aircraft.
Information provided by AIS equipment, such as unique identification, position, course, and speed, can be displayed on a screen or on an electronic chart display and information system (ECDIS). AIS is intended to assist a vessel's watchstanding officers and to allow maritime authorities to track and monitor vessel movements. AIS integrates a standardized VHF transceiver with a positioning system such as a Global Positioning System receiver, with other electronic navigation sensors, such as a gyrocompass or rate of turn indicator.
The International Maritime Organization's International Convention for the Safety of Life at Sea requires AIS to be fitted aboard international voyaging ships with , and all passenger ships regardless of size. For a variety of reasons, ships can turn off their AIS transceivers. As of 2021, there were more than 1,644,000 ships equipped with AIS.
AIS offers essentially no security and relies on the cooperation of the participants and on the enforcement of its rules by law and on plausibility evaluation.
Viewing and using AIS data AIS is intended, primarily, to allow ships to view marine traffic in their area and to be seen by that traffic. This requires a dedicated VHF AIS transceiver that allows local traffic to be viewed on an AIS enabled chartplotter or computer monitor while transmitting information about the ship itself to other AIS receivers. Port authorities or other shore-based facilities may be equipped with receivers only, so that they can view the local traffic without the need to transmit their own location. All AIS transceivers equipped traffic can be viewed this way very reliably but is limited to the VHF range, about 10–20 nautical miles.
If a suitable chartplotter is not available, local area AIS transceiver signals may be viewed via a computer using one of several computer applications such as ShipPlotter, GNU AIS or OpenCPN. These demodulate the signal from a modified marine VHF radiotelephone tuned to the AIS frequencies and convert into a digital format that the computer can read and display on a monitor; this data may then be shared via a local or wide area network but will still be limited to the collective range of the radio receivers used in the network. Because computer AIS monitoring applications and normal VHF radio transceivers do not possess AIS transceivers, they may be used by shore-based facilities that have no need to transmit or as an inexpensive alternative to a dedicated AIS device for smaller vessels to view local traffic but, of course, the user will remain unseen by other traffic on the network.
A secondary, unplanned and emerging use for AIS data is to make it viewable publicly, on the internet, without the need for an AIS receiver. Global AIS transceiver data collected from both satellite and internet-connected shore-based stations are aggregated and made available on the internet through a number of service providers. Data aggregated this way can be viewed on any internet-capable device to provide near global, real-time position data from anywhere in the world. Typical data includes vessel name, details, location, speed and heading on a map, is searchable, has potentially unlimited, global range and the history is archived. Most of this data is free of charge but satellite data and special services such as searching the archives are usually supplied at a cost. The data is a read-only view and the users will not be seen on the AIS network itself. Shore-based AIS receivers contributing to the internet are mostly run by a large number of volunteers. AIS mobile apps are also readily available for use with Android, Windows and iOS devices. See External links below for a list of internet-based AIS service providers. Ship owners and cargo dispatchers use these services to find and track vessels and their cargoes while marine enthusiasts may add to their photograph collections.Top User Photos, Vessel Tracker Community. Retrieved October 14, 2008.
Deployment history At the simplest level, AIS operates between pairs of radio transceivers, one of which is always on a vessel. The other may be on a vessel, on-shore, or on a satellite. Respectively, these represent ship to ship, ship to shore, and ship to satellite operation and follow in that order.
Vessel-based AIS transceivers The 2002 IMO SOLAS Agreement included a mandate that required most vessels over 300GT on international voyages to fit a Class A type AIS transceiver. This was the first mandate for the use of AIS equipment and affected approximately 100,000 vessels.
In 2006, the AIS standards committee published the Class B type AIS transceiver specification, designed to enable a simpler and lower-cost AIS device. Low-cost Class B transceivers became available in the same year triggering mandate adoptions by numerous countries and making large-scale installation of AIS devices on vessels of all sizes commercially viable.
Since 2006, the AIS technical standard committees have continued to evolve the AIS standard and product types to cover a wide range of applications from the largest vessel to small fishing vessels and life boats. In parallel, governments and authorities have instigated projects to fit varying classes of vessels with an AIS device to improve safety and security. Most mandates are focused on commercial vessels, with leisure vessels selectively choosing to fit. In 2010, most commercial vessels operating on the European Inland Waterways were required to fit an Inland waterway certified Class A, all EU fishing boats over 15m must have a Class A by May 2014, and the US has a long-pending extension to their existing AIS fit rules which is expected to come into force during 2013. It is estimated that as of 2012, some 250,000 vessels have fitted an AIS transceiver of some type, with a further 1 million required to do so in the near future, and even larger projects under consideration. 1
Terrestrial-based AIS (T-AIS) T-AIS refers to communication between ships and between ships and near-coast land stations. T-AIS range is approximately limited by line of sight, typically to a maximum of about and for a land based station visibility is lost beyond coastal waters. In addition to port and maritime authority operated transceivers, there is a large network of privately owned ones as well.
T-AIS is sufficient for ship collision avoidance, but does not allow for the comprehensive collection of global AIS data.
Satellite-based AIS (S-AIS) In the 1990s, AIS was not anticipated to be detectable from space. But AIS has much longer vertical than horizontal reach and can be received by satellites in low Earth orbit with altitudes above 500km. The reuse of frequencies by senders which are out of view of each other on the surface, but simultaneously in view of a satellite, creates the principal technical challenge for the reliable reception of AIS messages by satellite. In other words, the detection footprint of a satellite is much larger than the AIS network cell size. S-AIS could enable truly global AIS coverage, but because of its limitations will never match the reception performance and near-zero latency of the terrestrial network. Satellites augment rather than replace the terrestrial system.
Since 2005, various entities have been experimenting with detecting AIS transmissions using satellite-based receivers and, since 2008, companies such as L3Harris, exactEarth, ORBCOMM, Spacequest, Spire and also government programs have deployed AIS receivers on satellites.
The two nCube cubesats built by Norwegian university students (nCube-2 launched October 27, 2005 and nCube-1 launched July 26, 2006) were both failures. They would have attempted to track ships and an AIS-carrying reindeer.
+ No Mission Launch Organization Orbit Period Perigee Apogee Inclination Weight minutes km kg 1 TacSat-2 Dec 2006 USAF AFRL Circular 92.9 413 424 40° 367 2 CanX-6 (EV-0) Apr 2008 COM DEV SSO 96.9 604 626 97.6° 6.5 3 Orbcomm CDS-3 Jun 2008 Orbcomm Circular 97.8 653 663 48.5° 80 4 AprizeSat-3 Jul 2009 Aprize SSO 96.8 562 686 98.3° 12 5 AprizeSat-4 6 Rubin-9.1 Sep 2009 LuxSpace 99.9 720 799 98.0° 8 7 Rubin-9.2 8 Sumban dilaSat SunSpace/CSIR 92.4 401 402 97.1° 82 9 AISSat-1 Jul 2010 FFI 96.9 610 624 98.1° 7 10 ResourceSat-2 (EV-2) Apr 2011 ISRO 101.3 813 825 98.8° 1,200 11 AprizeSat-5 (EV-5) Aug 2011 exactEarth 97.8 828 693 98.3° 12 12 AprizeSat-6 (EV-6) 13 VesselSat-1 Oct 2011 LuxSpace Circular 102 853 873 20° 29 14 VesselSat-2 Jan 2012 SSO 94 472 484 97.5° 29 15 SDS-4 May 2012 JAXA 97.9 662 671 98.4° 50 16 ExactView-1 (EV-1) Jul 2012 exactEarth 101 811 827 99.1° 100 17 AAUSAT3 Feb 2013 Aalborg University 100 771 789 98.5° 0.8 18 AprizeSat-7 (EV-5R) Nov 2013 exactEarth 97 594 654 97.6° 12 19 AprizeSat-8 (EV-12) 595 670 97.6° 12 20 AprizeSat-9 (EV-11) Jun 2014 98 618 719 97.8° 12 21 AprizeSat-10 (EV-13) SpaceQuest 618 737 97.8° 12 22 AISSat-2 Jul 2014 FFI 97.1 625 632 98.4° 7 23-28 6xOG2 Orbcomm Circular 99 715 719 47° 216 29 ExactView-9 (EV-9) Sep 2015 exactEarth Equatorial 97.5 642 653 6° 5.5 30-40 11xOG2 Dec 2015 Orbcomm Circular 99 715 719 47° 216 41 M3MSat (EV-7) Jun 2016 Canadian Govt. SSO 94.7 502 519 97.4° 95 42 NorSat-1 Jul 2017 NSC 96.6 593 610 97.6° 30 43 NorSat-2 16 44 GOMX-4A Feb 2018 Gom Space 94.5 489 515 97.3° 45 GOMX-4B
On December 16, 2006, Air Force Research Laboratory's TacSat-2 was launched and became the first satellite to successfully capture AIS signals. It featured a phased array antenna.
On July 29, 2009, SpaceQuest launched AprizeSat-3 and AprizeSat-4. Both were commissioned one hour after separation and began collecting data on their second orbit. In the first 160 minutes, 200,000 AIS messages were captured. They were able to receive the U.S. Coast Guard's SART test beacons off of Hawaii in 2010. In July 2010, SpaceQuest and exactEarth of Canada announced an arrangement whereby data from AprizeSat-3 and AprizeSat-4 would be incorporated into the exactEarth system and made available worldwide as part of their exactAIS(TM)service.
On June 1, 2010, the NORAIS SDR receiver onboard the International Space Station (apogee: 422km) was switched on and was a technology demonstration success: on a typical good day 400,000 position reports were receivable from 22,000 senders. An October 2011 report stated a total of 110 million received messages from 82,000 unique MMSI numbers. NORAIS-1 had received a total of 350 million AIS messages from 142,000 unique ships during 213 weeks in operation when it was replaced with the NORAIS-2 hardware upgrade on February 1, 2015. NORAIS-2 could receive all four AIS channels simultaneously.
In 2009, ORBCOMM launched AIS enabled satellites in conjunction with a US Coast Guard contract to demonstrate the ability to collect AIS messages from space. In 2009, Luxspace, a Luxembourg-based company, launched the RUBIN-9.1 satellite (AIS Pathfinder 2). The satellite is operated in cooperation with SES and REDU Space Services. In late 2011 and early 2012, ORBCOMM and Luxspace launched the Vesselsat AIS microsatellites, one in an equatorial orbit and the other in a polar orbit (VesselSat-2 and VesselSat-1).