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Automatic identification system
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<p>The automatic identification system (AIS) is an automatic tracking system that uses <a href="/facts/Transceiver/S6HSzRPf">transceivers</a> on ships and is used by <a href="/facts/Vessel_traffic_service/TC6naQVe">vessel traffic services</a> (VTS). When satellites are used to receive AIS signatures, the term <i>Satellite-AIS</i> (S-AIS) is used. AIS information supplements <a href="/facts/Marine_radar/G5h3tyk0">marine radar</a>, which continues to be the primary method of <a href="/facts/Collision/0a3WSqod">collision</a> avoidance for water transport. Although technically and operationally distinct, the <a href="/facts/ADS-B/WSUFghq4">ADS-B</a> system is analogous to AIS and performs a similar function for aircraft. </p><p>Information provided by AIS equipment, such as unique identification, <a href="/facts/Coordinate_system/Mtd0q4SP">position</a>, <a href="/facts/Course_(navigation)/CWexuXNF">course</a>, and speed, can be displayed on a screen or an <a href="/facts/Electronic_chart_display_and_information_system/67MvKTsM">electronic chart display and information system</a> (ECDIS). AIS is intended to assist a vessel's <a href="/facts/Watchstanding/RRDoNdRm">watchstanding</a> officers and allow <a href="/facts/Sea/7eo8zrRW">maritime</a> authorities to track and monitor vessel movements. AIS integrates a <a href="/facts/Standardization/vS9AhNMS">standardized</a> <a href="/facts/Very_high_frequency/8V90M1Sl">VHF</a> transceiver with a positioning system such as a <a href="/facts/Global_Positioning_System/DKVLnzF3">Global Positioning System</a> receiver, with other electronic navigation sensors, such as a <a href="/facts/Gyrocompass/nS0m2Pod">gyrocompass</a> or <a href="/facts/Rate_of_turn_indicator/veJ3YMAf">rate of turn indicator</a>. Vessels fitted with AIS transceivers can be tracked by AIS base stations located along coastlines or, when out of range of terrestrial networks, through a growing number of satellites that are fitted with special AIS receivers which are capable of deconflicting a large number of signatures. </p><p>The <a href="/facts/International_Maritime_Organization/7mzxd3B5">International Maritime Organization</a>'s <a href="/facts/International_Convention_for_the_Safety_of_Life_at_Sea/U0nuz5BL">International Convention for the Safety of Life at Sea</a> requires AIS to be fitted aboard international voyaging ships with 300 or more <a href="/facts/Gross_tonnage/uK5N7oGL">gross tonnage</a> (GT), and all passenger ships regardless of size. For a variety of reasons, ships can turn off their AIS transceivers. </p>