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AIS Facts:
What does AIS stand for? Automatic Identification System
What is the purpose of AIS? AIS is a shipboard VHF broadcast system that transmits and receives information pertinent to safe navigation of ships and to enhance port security. The data may be shown on the AIS display or Radar/ECDIS equipment. Shore stations (VTS) will eventually have AIS and will be able to coordinate and control AIS channel assignments.
What does the "U" in U-AIS stand for? “U” stands for "Internationally" Universal AIS, as opposed to some previous AIS systems, which were proprietary or unique to a specific area. UAIS Systems are designed in compliance with IMO Resolution MSC.74(69) Annex 3, Part 2.
How does AIS work? Each AIS system consists of one VHF transmitter, two VHF TDMA receivers, one VHF DSC receiver, and a communications link (IEC 61162/NMEA 0183) to shipboard display and sensor systems. Static and dynamic Navigational data is sent via VHF from ship to ship using SOTDMA. Position and timing information is normally received from an internal or external global navigation satellite system (e.g. GPS) receiver, including a DGPS receiver for precise position in coastal and inland waters. Other information broadcast by the AIS, if available, is electronically obtained from shipboard equipment through standard marine data connections.
What type of data needs to be entered into the AIS system by the operator? MMSI number, call sign, ship’s name, etc. must be entered when the unit is first installed. Voyage data, such as destination, crew size and cargo are entered before starting a voyage. Users may enter short safety-related messages as needed.
What sensors must be connected to AIS? For IMO SOLAS class ships, the AIS system should have ship’s position, course over ground, speed over ground and heading. Rate of turn must be input if it is available. (R-O-T data is voluntary, if it is not available on the vessel.) Ship’s position, course over ground and speed over ground should be supplied from an IMO compliant GPS receiver. Heading should be supplied from gyrocompass. For vessels required to carry AIS due to the Maritime Security Act of 2002, contact your local USCG Marine Safety Office for the latest information on AIS regulations.
What is the purpose of the AIS system’s internal DSC capability? In an area where an AIS channel is not found, the DSC will be used to communicate with VTS stations to determine the appropriate frequency to be used as an alternate AIS channel.
Are there any special power supply requirements? Yes. IMO regulations state that AIS should be connected to emergency power.
Are both internal and external GPS necessary for AIS? For vessels mandated to carry AIS by the IMO, an external GPS input is required. The internal GPS is used as a clock for UTC for synchronization, and the external GPS is necessary as the sensor for L/L, COG and SOG dynamic data. For vessels in the U.S. required to carry AIS due to the U.S. Maritime Security Act of 2002, contact your Local USCG Marine Safety Office for the latest information on U.S. AIS regulations.
Are there any installation guidelines available? Yes. The IMO has published some installation guidelines. Can be found at http://www.navcen.uscg.gov/marcomms/imo/Circulars/IMO.SN.Circ.227_AIS_Installation.pdf
Should Differential GPS be used? It may be used, but is not required by the IMO. Some authorities (i.e. The St. Lawrence Seaway Management Corporation) recommend transmitting DGPS data by AIS.
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