Automatic Identification System

The term Automatic Identification System (AIS; into German: Automatic Identification System) or Universal Automatic Identification System ( UAIS ) refers to a radio system that improves through the exchange of navigation and other ship data security and the steering of the ship traffic. It was developed by the International Maritime Organization (IMO ) adopted on 6 December 2000 as a binding standard.

Benefits, limitations,

AIS is used according to the performance standard ( Performance Standard ) of the International Maritime Organization (IMO ) for the following purposes:

• The Collision between ships
• Gain as a means for coastal states, information about ships and their cargo
• As a tool for land-based monitoring and traffic organization ( VTS).

AIS improves the planning and decision-making on board, as not only position, course and speed of the surrounding ships to be transferred, but also ship data ( vessel name, MMSI number, call sign, etc.). This facilitates, for example, agreements between skippers by radio. AIS operates independently of the limitations of the optical point of view and the radar wave propagation (eg, occlusions or shadows ), so that ships can be identified that are located behind a cape or behind a flow curve, provided that the broadcast on the FM band signals penetrate.

AIS is referred to as an active system. For his use of an active, technically functional unit is a prerequisite, as opposed to a passive radar system.

Demarcation

When considering AIS is to distinguish between the AIS system itself ( the radio-based data transfer) and the presentation of information that are transferred by AIS. A presentation on board can be done for example in an ARPA - plant or in an electronic chart (ECDIS ); However, these devices do not belong to the AIS system. For AIS - board equipment is prescribed as a display and control element merely a so-called "Minimum Keyboard and Display" ( MKD). A wise use of AIS data is a useful representation in an appropriate display, along with other navigational information relevant advance.

Mandatory equipment

The carriage requirements for ships engaged in international trade is regulated by the International Convention for the Safety of Life at Sea ( SOLAS). Since 1 January 2004 all commercial vessels over 300 gross tonnage engaged on international voyages and since 1 July 2008 are also those over 500 GT in national voyages obliged to operate an AIS system in maritime transport. Also have ships that are longer than 20 m or more than 50 passengers on board, must be fitted with an AIS - board equipment. The equipment requirement has been introduced for new ships July 1, 2002 and for existing ships as of 2004. Do not fall under the provisions of SOLAS warships, but most vessels with an AIS - board device, wherein the transmitter is switched off, equipped. For traditional ships national exceptions may apply.

For barges the SOLAS regulations also do not apply here, a mandatory requirement on the basis of regulations of the European Union, give the Central Commission for Navigation on the Rhine or national regulations. For example exists for inland waterway vessels ( except for small vehicles) since 1 July 2008 in the Austrian part of the Danube between the current kilometers 1880.2 and 2199.3 and some adjacent waters a mandatory option with Inland AIS transceivers.

In Turkey, discussed just a mandatory equipment for pleasure boats.

Facilities

Class A transceiver

Class A transceivers are designed for commercial vessels ride. They are on all vehicles over 300 gross tonnage engaged on international voyages and for certain passenger vessels subject to the SOLAS Convention, prescribed. Class A transceivers transmit at a higher VHF signal strength as a Class B transceivers and can therefore be received from more distant ships and also send messages more often. The transmitter adjusts the repetition frequency of the transmission of the vehicle speed and the maneuver status.

Inland AIS transceiver

Inland AIS transceivers are required for AIS equipped vessels on the Rhine transceiver, if it is not a ship. The equipment complies with the Class A transceivers with extensions for inland navigation.

Class B transceiver

Class B transceivers are in many respects with Class A transceivers comparable, due to less stringent performance requirements, but usually cheaper. Class B transceivers transmit at a lower signal strength and a lower reporting rate. They can be used by all equipment not requiring vessels eg in the leisure industry and the fishery.

AIS base stations

AIS base stations are a part of the land-based AIS infrastructure and eg ship traffic systems (VTS ) are used. They serve both to capture the traffic in the areas they cover it overseas territory, on the other hand, these devices can the transmission of AIS transceivers on board specifically controlled (among so-called " polling " or raising the reporting rate ).

AtoN transceiver ( Aids to Navigation )

AtoNs are transceivers that can be installed on buoys and other aids to navigation and data regarding the type, name and position of the vessel crossing sign emit. A special form is the virtual (apparent) AtoN; in principle, a " sham " by transferring the corresponding messages ( physically nonexistent ) navigation signs.

AIS transceiver for search and rescue aircraft

A special mobile device type is intended for use on board aircraft, which are involved in search and rescue at sea (SAR ).

AIS receiver

AIS receivers receive transmissions from AIS transceivers in the area, but will send as the name of the receiver suggests, no data.

Technical standards

The basic technical standard for AIS is called ITU -R M.1371 -3 " Technical characteristics for a universal Shipborne automatic identification system using time division multiple access in the VHF maritime mobile band" and is published by the International Telecommunication Union.

AIS transmits alternately on two channels in the VHF Seefunkbereich:

Transmitting the AIS data occurs in a fixed time frame. Per minute are 2250 time slots ( slots) available to the AIS transceiver is synchronized via its integrated GPS receiver. Class A transceiver tune the slot assignment independently with located within radio range of other off ( SOTDMA = Self Organising Time Division Multiple Access ), while Class B transceiver use free time slots to their data to send ( CSTDMA = Carrier Sense Time Division Multiple Access).

As each tuned antenna for the VHF marine band antenna can be used. Especially suitable are special combined FM / GPS antennas for AIS containing both antennas required for AIS transceiver in an assembly.

The dynamic ship information Position ( LAT, LON), course (COG ), speed ( SOG ) and time ( UTC) receives the AIS transceiver from the integrated GPS receiver in Class A by the navigation system of the ship. The course direction ( heading ) can be fed via a NMEA -183 interface from the compass as HDG record.

Equipment subject to vessels shall have Class A equipment with a pilot port, a standardized data interface according to EIA -422 in a readily accessible location that allows, for example, pilots to access with their own equipment on the traffic situation and its own navigation data. Due to faulty installation errors in the pin assignment of the connector can be corrected in the on-board installation usually by commercially available adapters without intervention.

Types of messages, AIS messages

To ensure the global usability of AIS data transmitted with, the International Telecommunication Union has defined a total of 22 types of messages or telegrams in their standard ITU R M.1371, which were standardized in their structure down to the last bit. Each AIS unit must receive these frames and can send out, provided for each device type ( see above under " Assets") of this telegram is " allowed". The most important message types are:

• ID # 1: regular position report of a class -A transceiver
• ID # 4: report of a base station
• ID # 5: regular reporting of ships and dates of a class -A transceiver
• ID # 9: Position report of a SAR aircraft
• ID # 12: safety- related message - addressed
• ID # 14: safety- related message - to all
• ID # 18: regular position reporting a Class B transceiver
• ID # 21: Position and status message of AtoN transceiver

Other message types:

• ID # 24: Static ship data sent from Class B, C, S Tranceivern

Can be defined via the above telegrams, other types of telegrams with extended purpose ( eg weather reports ) internationally or regionally via the method of so-called " International Application Identifier " (IAI ) or " Regional Application Identifier " ( RAI). As a container for the transmitted message content using this method, the standardized message of the binary message (binary message, ID # 6, # 8) will be used.

Ship data

The AIS unit sends in the form of the above-mentioned telegrams ship-specific data that can be received and evaluated by each AIS receiver in range:

For Inland AIS still comes to:

The navigational status and the dates need to be updated manually by the officer of the watch. But it must not be sending data. Only vessel name, MMSI, position, course and vessel size are often sent Especially with class B transmitters of the recreational marine environment.

Sending the AIS data

The AIS signals are on two FM Seefunkkanälen (usually on AIS1 and AIS2, ie VHF Channel 87B and 88B with the frequencies 161.975 MHz and 162.025 MHz) sent with HDLC protocol data in a fixed time frame. Through appropriate software or devices, the data is decoded and displayed graphically for example as text information or similar in a radar image.

The intervals at which a ship sends its data, depend on the speed and the price rate of change of the ship and of his maneuvers status ( in service, anchored or moored ) from.

Use of AIS data on board

As described in chapter " demarcation " explains, it is at AIS is a system for data transmission. Prescribed part of the AIS system on board is a so-called "Minimum Keyboard and Display" ( MKD). The following statements relate to the use of AIS data in the context of navigation systems such as in an ARPA - plant or in an electronic chart ( ECDIS). These are not part of the actual AIS system.

The current traffic situation is displayed dynamically, each ship movement is visible on the screen. In addition, it shows when exactly two encounters ships have the shortest distance from each other how great this will be and how long it will take until then (CPA = closest point of approach / TCPA = time to CPA).

The advantage of the AIS relative to the radar, among other things, that the officer on duty knows the identity of other ships and course and speed changes are sent automatically when fast maneuvers. He can also contact via marine radio and deny necessary maneuvers.

With AIS also ship movements can be captured behind larger obstacles during the channel navigation; the radar is often overwhelmed in such situations, since ships in radar shadows are not included. The FM signals of the AIS achieve these shadow areas much better due to the longer wavelength. On inland waterways are situated in foreclosed for radio signals curves transceivers that transmit the AIS signals also over mountains.

The ship data can be directly integrated into the electronic chart or processed by a separate AIS software on the computer to represent all ship movements including his own position. A separate software often provides a clearer representation, the display of additional common on AIS data ( in testing: weather reports, water levels ) and better support for collision.

Smaller equipment not subject to marine vessels, the AIS data use passive with inexpensive AIS receivers and display position, course and speed of the surrounding equipped ships. The received data can be displayed on a small screen on the receiver, on a purpose-built existing plotter or with the appropriate software on a separate laptop / computer. You can then timely evasive action to prevent crashes, especially in poor visibility, initiate.

But AIS can not replace radar since about military vehicles often do not send AIS signals and many smaller vehicles are not equipped with an AIS transceiver. The reported data is not always reliable.

Range

Ultra-short waves have a range that is only slightly exceeds the geometrical visibility. This depends on the antenna height; this is called a quasi- optical signal propagation. For ship - to-ship connections of these about 20 nautical miles ( 37 km). Received coastal stations depending on antenna height signals from ships within 50-100 km. AIS base stations are usually equipped with highly collimating antenna ( directivity ) and mounted higher than is possible on board, so that there are greater ranges here.

Low flying satellites can receive FM signals, provided that the antennas radiate and upwards ( omni-directional). Orbcomm equips its new satellites with AIS receivers. If the test is successful, the system could capture all ships worldwide.

In November 2009, an AIS receiver antenna was on the European part of the ISS, the Columbus module installed. Since June 1, 2010 are under an ESA study reception attempts with different AIS receivers. Interfering signal overlap due to the large distance to radio horizon is countered with special signal processing techniques.

Aircraft, navaids, land station

Besides vessels are also involved in the AIS:

• SAR aircraft
• Distress marker transmitter (AIS SART - Search and Rescue Transmitter)
• Some navaids ( Aids to Navigation / AtoN )
• Level and Weather Stations
• Country of traffic monitoring stations (VTS )

In brief, traffic control

About the AIS can also be set by the IMO short messages and free text messages ( "safety related messages" ) are transmitted; this telegram is internationally standardized ( see above " telegrams "). About the mechanism of IAI / RAI for example, the automated measuring stations on navaids current weather conditions, water level and flow data are distributed or route instructions will be sent to ships in addition. On rivers and canals, especially in the field of locks and constrictions, the AIS is increasingly being used for traffic control to display, for example, the opening of the sluice.