Silent VTSIn some areas of the world e.g. rivers and low traffic areaswhere the traffic density don’t justify VTS, an idea called”Selent VTS” has evolved. Instead of installing conventionalVTS’s on shore the <strong>AIS</strong> equipped ships will acct as their ownVTS’s and use the <strong>AIS</strong> to get their situation awareness.Display presentationThe <strong>AIS</strong> provides several possibilities for displaying the <strong>AIS</strong>information. The minimum required display is a three linealpanumeric display that presents bearing, distance, name andall other information in a spread sheet format, enabling theOOW to make manual inputs and to identify a ship by comparingbaring and range from the radar PPI. Most probably theminimum display will be very rarely used. Many ECDIS manufacturesare today implementing the <strong>AIS</strong> symbols in theirequipments. Manufactures, as ADVETO, STN ATLAS,TRANSAS MARINE, ANS, ICAN are already handling the<strong>AIS</strong> in their softwares.It is sometimes not possible to present the <strong>AIS</strong> informationon an old radar screen but the new performance standard forradar which is developed by IMO includes presentation of <strong>AIS</strong>information. <strong>AIS</strong> targets, superimposed on the radar display,will inform the operator weather the targets are <strong>AIS</strong> equippedor not.IEC has a draft proposal for <strong>AIS</strong> symbology to display onECDIS and or ENC systems.To reduce clutter on the radar or the ECDIS display, due totoo many <strong>AIS</strong>’s appearing at the same time the <strong>AIS</strong> symbolscould be “Active” or “Sleeping”.● “Active” means that a triangle is showing the targets headingand (if high accurate positions used) the COG/SOG vector.● “Sleeping” means that the mariner has chosen to suppressvectors and heading line and only a small green trianglepointing in the direction of the heading is shown. A sleepingtarget could always be activated if the mariner selects it.High update rateA modern ARPA radar is able to select and track 20 targetswith an update rate of 3 seconds. The symbol on the PPI willfollow the target, except when a target swap is appearing. Dueto the limitations of the ARPA, a course alteration of anothership will normally not be detected until one or two minutesafter the course change. For a large tanker it will take up to fiveminutes. Further more, another one or two minutes is neededfor the ARPA to present a reliable target vector with course andspeed through the water.It is obvious that a high update rate is needed for <strong>AIS</strong> targets,superimposed on a radar display. If the update rate is tooslow there will be situations, when using smaller ranges, wherethe <strong>AIS</strong> symbol will not catch up with the radar target.International standardisation for <strong>AIS</strong>Within ITUTechnical characteristics for a shipborne <strong>Automatic</strong> <strong>Identification</strong><strong>System</strong> (<strong>AIS</strong>) using TDMA in the VHF maritimemobile band has been defined by ITU in ITU-R M.1371-1Frequencies to be used for the universal shipborne <strong>AIS</strong> hasbeen defined in ITU-R M.1084-3.Within IMOPerformance standards has been defined in IMO resolutionMSC.74(69) Annex 3Carriage requirements in SOLAS was originally approved byMSC 72 and MSC 73. An implementation period from 2002to 2008 was allowed. In 2001 when the security aspects of <strong>AIS</strong>was highlighted, IMO decided on an accelerated implementationfor ships on international voyages.<strong>Automatic</strong> identification systems (<strong>AIS</strong>)All ships of 300 gross tonnage and upwards engaged oninternational voyages and cargo ships of 500 gross tonnageand upwards not engaged on international voyages andpassenger ships, irrespective of size, shall be fitted with <strong>AIS</strong>,as follows:1. ships constructed on or after 1 July 2002;2. ships engaged on international voyages constructed before1 July 2002;● in the case of passenger ships not later than 1 July 2003;● in the case of tankers, not later than the first SafetyEquipment Survey after 1 July 2003;● in the case of ships, other than passenger ships andtankers, of 300 gross tonnage and upwards, not laterthan 31 Dec 2004;3. ships not engaged on international voyages constructedbefore 1 July 2002, not later than 1 July 2008. However, inSweden a faster implementation is required, starting in 2003and ending 2007.4. The Administration may exempt ships from the applicationof the requirements of this paragraph when such ships willbe taken permanently out of service within two years afterthe implementation date specified in paragraph 1. [Additionally,an Administration may exempt vessels flying its flagin its domestic trade from carrying <strong>AIS</strong> when operating inareas where in the judgement of the Administration the densityof shipping does not justify <strong>AIS</strong>].<strong>AIS</strong> shall:● provide automatically to appropriately equipped shorestations, other ships and aircraft information, including theship’s identity, type, position, course, speed, navigationalstatus and other safety-related information;● receive automatically such information from similarly fittedships;● monitor and track ships; and● exchange data with shore-based facilities. The requirementsof this paragraph shall not be applied to cases where internationalagreements, rules or standards provide for the protectionof navigational information. <strong>AIS</strong> shall be operated takinginto account the guidelines adopted by the Organization.Within IECIEC Technical Committee TC80 is now working hard to definethe test standard for a simplified <strong>AIS</strong> for non SOLAS-ships.6 <strong>AIS</strong> for ships in the future
The principle of <strong>AIS</strong> STDMA/ITDMAEach time slotrepresents26.6milliseconds.The <strong>AIS</strong> of ship Asends the positionmessage in one timeslot. At the sametime it reservesanother time slot forthe next positionmessage.The sameprocedure isrepeated by allother <strong>AIS</strong>equippedships.Ship BShip CShip AShips with a self organizing broadcast <strong>AIS</strong> onboard will see each other as soon as they are in radio range.National and regional <strong>AIS</strong> systemsAn <strong>AIS</strong> network covering the Swedish coastal waters and thelarge lakes was established in 1997. The system was improvedand updated in 2001. The information from this network isavailable to the Swedish Maritime Administration for use inVTS:s, MRCC, pilot stations, Icebreaking Operation Centeretc. Other Swedish administrations needing information on thesea traffic also have access to this information.The Helsinki Commission, working with protection of theenvironment in the Baltic area, decided in 2001 that all thecoastal states of the Baltic shall establish landbased <strong>AIS</strong> stationsand exchange the information from these stations. The preparationfor that is under way and presently Sweden, Norway,Finland and Russia are exchanging <strong>AIS</strong> information viaInternet connections. The information will also be collectedand stored by a central server for creation of traffic statistics forthe Baltic Sea.The European Union requires in a Directive the member statesto establish shorebased <strong>AIS</strong> system before 1 July 2007.<strong>AIS</strong> for ships in the future 7
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