AIS Automatic Identification System PDF

## Electronic Navigation ### 2.5 Automatic Identification System (AIS) **Figure 2.17 - AIS Receiver Display** AIS, also known as UAIS (Universal Automatic Identification System), is a VHF based shipboard transponder that is used for information exchange from: * **Ship to shore** * To obtain i...

## Electronic Navigation ### 2.5 Automatic Identification System (AIS) **Figure 2.17 - AIS Receiver Display** AIS, also known as UAIS (Universal Automatic Identification System), is a VHF based shipboard transponder that is used for information exchange from: * **Ship to shore** * To obtain information about a ship, its cargo and any other relevant information for the control and monitoring of traffic in VTS * **Ship to ship** * To aid identification of targets for navigational safety and maritime security. ### 2.5.1 AIS Carriage Requirements The IMO requires all passenger ships, other ships above 300GT engaged on international voyages and those above 500GT not engaged on international voyages to be fitted with AIS. The AIS must meet certain performance standards, ie: * It should transmit information that includes the ship's identity, type, position, course, speed, navigational status and other safety information automatically to appropriately equipped shore stations, other ships and aircraft * It should automatically receive information from similarly fitted ships * It must monitor and track ships * It must exchange data with shore-based facilities. ### 2.5.2 Components of the AIS The basic components of an AIS system are: * Satellite position fixing system, eg GPS * a VHF transceiver capable of operating on a frequency range between 156.025 to 162.025MHz on universally allocated VHF channels CH87B (161.975MHz) and CH88B (162.025MHz) * a computer to process and store the information. The three components are integrated to provide an automatic reception and broadcast of the information for all stations within the VHF range to receive. Other shipboard equipment that can be connected to AIS to display target station information are: * Ship's log * gyro/magnetic compass * ECDIS * radar * rate of turn (ROT) indicator * DSC receiver * VDR * INMARSAT or other long range communication equipment. The AIS equipment provides the following information: * Target station identity and position range, bearing and name of ship * information about all stations that are detected (or are within AIS range) * in graphical format (as shown in Figure 2.18) the AIS should display position, course and speed over the ground, heading, position of targets in relation to observing the ship. Various symbols are used by different manufacturers to show differences in targets such as those used on ARPA. The following five types of symbols are used on either the AIS graphical display or an attached ARPA or ECDIS: **Figure 2.18 - Symbols Used in Graphical Presentation** * **sleeping target** is used when no action to avoid a collision is required and is shown in Figure 2.18(A). The direction of the apex of the triangle is the target's heading * **activated target** is used when action to avoid a collision may be required and is shown in Figure 2.18(B). The additional information shown with this symbol is a vector representing a course and speed over ground, a second vector indicating the heading of the target and a small vector at the tip of the heading vector to show the rate of turn (if available) * **selected target** is used when the user needs more information by manually selecting of the target from the AIS equipment. The additional information such as CPA, TCPA will be also shown on the AIS display. It is shown on screen in Figure 2.18(C). * **dangerous target** is used when in breach of the preset CPA and TCPA limits set by the user, as shown in Figure 2.18(D) * **lost target** is used when the AIS signal is lost; its last position received is displayed with the symbol shown in Figure 2.18(E). ### 2.5.3 AIS Messages The information included below is transmitted every 2 to 10 seconds when underway and every 3 minutes when anchored: * MMSI number * navigational status * rate of turn * speed * position * course * true heading * time - UTC at which this information was processed. In addition, the following information is transmitted every 6 minutes: * MMSI number * IMO number * radio call sign * name of ship * type of ship * type of cargo * dimensions of the ship * location on the ship of the antenna used for position fixing * type of position fixing device * draught of the ship * destination of the ship * UTC of ETA at destination * on passenger vessels, the number of people onboard. ### Static Information When new AIS equipment is installed onboard ship, the following information is programmed into it: * Maritime Mobile Service Identity (MMSI) number * IMO vessel number * radio call sign * name of ship * type of ship * length and beam of the ship * location on the ship of the antenna used for position fixing. The IMO number, MMSI number and other similar controls are protected against misuse by passwords. ### Dynamic Information This is information that changes. | Information | Source | |---|---| | Ship's position with an indication of its accuracy | Automatically from GPS, position accuracy is approximately 10 m | | UTC of information update | Automatically from GPS | | Course and Speed over Ground | Optional, but, if available, may be provided from GPS or ship's Logs and Steering Compass | | Heading | Automatically from heading sensors from instruments such as Satellite, Gyro or Magnetic Compass | | Navigational status | Manually updated by OOW as required; the items that need to be updated can be selected from a list of items such as underway at anchor, not under command, aground, engaged in fishing | | Rate of turn (ROT) | Optional but, if available, may be provided by ROT sensors or gyrocompass. | **Table 6 - Dynamic Information** ### Voyage Related Information This information changes from voyage to voyage and so must be entered manually by the Watchkeeping Officers at the start of each voyage. Items to be updated are: * Ship's draught * type of hazardous cargo (if any) such as Dangerous Goods (DG), Harmful Substances (HS) and Marine Pollutants (MP) * destination and the ETA * route plan, ie the waypoints that ships will follow to the destination. ### Safety Related Information This information is entered manually and may be sent to either individual or all stations. The safety messages can be related to: * Navigational aids or marks such as buoys, beacons or lighthouses, etc * location, nature and other information about hazards that may present a threat to safety of navigation * information about the weather and other relevant phenomena. Alarms fitted on AIS are activated under the following circumstances: * When a target violates the set limits for CPA/TCPA * when a target is lost * in case of the failure of any sensor such as for course, speed, position or time sensor from the relevant instrument. ### 2.5.4 Considerations for use of AIS AIS is a valuable aid to navigation, particularly for reducing the time used for communication. It requires certain factors to be considered during its use: * Some types of vessels, such as warships, leisure craft and fishing vessels, may not be fitted with AIS. AIS is fitted on ships as part of mandatory carriage requirements and may be switched off in operational circumstances at the discretion of the Master. If a vessel's echo is visible on a radar screen but not indicated on AIS, it may be because the vessel is exempted from the carriage requirement or because its AIS is switched off. OOWs must keep in mind that there is a possibility that some targets may go undetected, even if fitted with AIS. * the absence of information on the AIS does not relieve the OOW of his duty to take action to avoid a collision. The guidance for use of AIS is the same as for VHF given in the relevant Merchant Shipping Notice - Dangers in the use of VHF in collision avoidance. Any action to avoid a collision should be taken in strict compliance with IRPCS * when using an overlay of AIS information on ECDIS, particular attention should be paid to the different datums in ECDIS, GPS and AIS. Ensure that the same datum is selected in both the GPS and AIS as for the chart * when using an overlay of AIS information on radar, the difference in datum may display echoes from AIS displaced from the true echoes painted by the radar itself * once the relevant information is updated in the AIS, it should operate, that is transmit and receive information, automatically without any further intervention of the OOW. The OOW should continue to monitor and carry out tests as per the manufacturer's instructions * an erroneous input of course, speed, rate of turn, etc will have the same consequences as when inaccurate information is used for a target in a radar plot. The OOW should frequently compare the ship's own data displayed on the AIS with the originating instrument * the OOW must keep in mind that AIS may not be able to detect targets in areas such as the blind or shadow sector, in rain or sea clutter or out of sight due to a bend or hidden behind a land mass. It is a valuable aid but should be used with extreme caution. **Additional information on the components of AIS can be found in Appendix 2.3**