Automatic Identification System

from Wikipedia, the free encyclopedia

The term Automatic Identification System ( AIS ; in German: Automatic Identification System ) or Universal Automatic Identification System ( UAIS ) describes a radio system that improves the safety and control of ship traffic by exchanging navigation and other ship data. It was adopted as a binding standard on December 6, 2000 by the International Maritime Organization (IMO).

Graphic display of AIS data (here on a website)

Benefits, limitations

According to the Performance Standard of the International Maritime Organization (IMO), AIS serves the following purposes:

  • collision prevention between ships
  • as a means for coastal states to obtain information about ships and their cargo
  • to monitor illegal fishing
  • as an aid for the land-based monitoring and control of traffic by traffic control centers (Vessel Traffic Service, VTS).

AIS improves planning and decision-making on board, as not only the position, course and speed of the surrounding ships are transmitted, but also ship data (ship name, MMSI number, radio call sign, etc.). This facilitates z. B. Agreements between skippers via radio. AIS works regardless of restrictions on the optical view and the propagation of radar waves (e.g. obscurations or shadows), so that ships that are behind a cape or a river curve can also be detected, provided that the signals emitted in the VHF frequency range penetrate.

AIS is called a cooperative system. An active, technically functional device is a prerequisite for its use, in contrast to radar as a self-sufficient system.

In addition to the originally intended goals, there are now services that process AIS data commercially and also offer it to the general public. The best-known providers of such AIS services include MarineTraffic and Vesseltracker . Furthermore, the AIS was used by Greenpeace to research illegal fishing .

Demarcation

When considering AIS, a distinction must be made between the AIS system itself (the radio-supported data transmission) and the representation of information that was transmitted via AIS. A representation on board can e.g. B. in an ARPA system or in an electronic nautical chart (ECDIS) ; however, these devices are not part of the AIS system. For AIS on-board devices, only a so-called “Minimum Keyboard and Display” (MKD) is required as a display and control element. A sensible use of AIS data requires a usable representation in a corresponding display, together with other navigationally relevant information.

Equipment obligation

The equipment requirement for ships in international voyage is regulated in the International Convention for the Safety of Life at Sea (SOLAS) . Since December 31, 2004, all commercial vessels over 300  GT on international voyages and since July 1, 2008 also those over 500 GT on national voyages have been obliged to operate an AIS system. The equipment requirement was introduced for new ships on July 1, 2002 and for existing ships from 2004. Warships do not fall under the regulations of SOLAS, but most warships are equipped with an AIS on-board device in which the transmitter can be switched off. For traditional ships national exemptions may apply.

The SOLAS regulations do not apply to inland waterway vessels either; here there may be an obligation to equip on the basis of regulations of the European Union, the Central Commission for Navigation on the Rhine or national regulations. For example, inland vessels (except for small craft) have been obliged to equip inland AIS transceivers on the Austrian part of the Danube between river kilometers 1880.2 and 2199.3 and some adjacent waters since July 1, 2008 .

On December 23, 2016, the use of Inland AIS was made mandatory on inland waterways within the scope of the Inland Waterways Regulations, for which electronic navigation maps for inland waterways ( IENC ) have already been published, and on the federal waterway of the Danube.

Investments

Class A transceiver

Class A transceivers are intended for commercial vessels. They are mandatory on all vehicles over 300 GT on international voyages and on certain passenger ships that are subject to the SOLAS Convention . The transmission power of Class A transceivers of up to 12.5 W is higher than that of Class B devices, so they can be received by ships that are further away. The transmitter adjusts the repetition frequency of the transmission of the speed of travel and the maneuver status and transmits more frequently than with class B devices.

Inland AIS transceiver

Inland AIS transceivers are compulsory for ships equipped with AIS transceivers on the Rhine , unless they are seagoing vessels. The devices correspond to class A transceivers with extensions for inland navigation.

Class B transceiver

Class B transceivers are comparable to class A transceivers in many ways, but are usually cheaper due to less stringent performance requirements. Class B transceivers transmit with a lower transmission power of maximum 2 W and a lower reporting rate. You can from all ships that do not require equipment, e.g. B. be used in the leisure sector and in fishing.

Class B transceivers send less data across the ship than class A transceivers. In particular, B-transmitters do not broadcast any information about the cargo or the destination of the trip. This also makes operation easier: after the ship's name and dimensions have been programmed once, no more settings need to be made on a Class B transceiver and they are therefore immediately active after switching on.

AIS base stations

AIS base stations are part of the shore-based AIS infrastructure and are used e.g. B. used by traffic control centers (Vessel Traffic Service, VTS). On the one hand, they are used to record the traffic in the sea area they cover, and on the other hand, these devices can control the transmission of AIS transceivers on board in a targeted manner (including so-called "polling" or increasing the reporting rate).

AtoN transceiver (Aids to Navigation)

Aten are transceivers that on tons can be installed and other aids to navigation and, for information. B. send out about the type, designation and position of the shipping sign. The virtual (apparent) AtoN is a special form; in principle a "faked" (physically non-existent) shipping mark by transmitting the corresponding messages. This technique is mainly used to mark restricted areas or hydraulic structures with a large area: A bucket with an active AIS transmitter is not placed on every corner position (usually marked by cardinal buoys or shipping buoys), but rather it is only on one bucket a transmitter that also transmits the positions of the other delimitation buoys.

AIS transceiver for search and rescue aircraft

A special type of mobile device is intended for use on board aircraft involved in the search and rescue service at sea (SAR) .

AIS receiver

AIS receivers receive transmissions from AIS transceivers in the vicinity, but, as the name receiver already suggests, do not transmit any data.

Technology, technical standards

Synchronization of the time windows

The basic technical standard for AIS is called ITU-R M.1371 "Technical characteristics for an automatic identification system using time division multiple access in the VHF maritime mobile frequency band" and is published by the International Telecommunication Union . Version 5 of the document is valid as of February 2014.

AIS transmits alternately on two channels in the VHF marine radio range:

AIS 1 - 161.975 MHz (channel 87B)
AIS 2 - 162.025 MHz (channel 88B)

The transmission of the AIS data takes place in a fixed time frame. 4500 timeslots are available per minute, 2250 per channel, to which an AIS transceiver is synchronized via its integrated GNSS receiver. Class A transceivers automatically coordinate the slot assignment with others within radio range (SOTDMA = Self Organizing Time Division Multiple Access), while class B transceivers use free time slots to send their data (CSTDMA = Carrier Sense Time Division Multiple access).

Any antenna tuned to the VHF marine radio band can be used as the antenna. Special combined VHF / GPS antennas for AIS, which contain both antennas required for an AIS transceiver in one assembly, are particularly suitable.

The AIS transceiver receives the dynamic ship data position (LAT, LON), course (COG), speed ( SOG ) and time (UTC) from the integrated GPS receiver, and in class A also from the ship's navigation system. The course direction (heading) can be fed in from the compass as an HDG data record via a NMEA 0183 interface.

Pilot port

Ships requiring equipment must have class A systems with a pilot port, a standardized data interface in accordance with EIA-422 at an easily accessible location. B. Permits pilots to access traffic situation and navigation data with their own equipment. Errors in the pin assignment of the plug that occur due to incorrect installation can usually be corrected using commercially available adapters without interfering with the on-board installation.

Message types, AIS telegrams

In order to ensure the global usability of the data sent with AIS, the International Telecommunication Union has specified a total of 22 message types or telegrams in its ITU R M.1371 standard, the structure of which has been standardized down to the last bit. Every AIS device must be able to receive and send these telegrams, provided that this telegram is "permissible" for the respective device type (see above under "Systems"). The most important telegram types are:

  • ID # 1: regular position report of a class A transceiver
  • ID # 4: Message from a base station
  • ID # 5: regular reporting of ship and voyage data of a class A transceiver
  • ID # 9: Position report of a SAR aircraft
  • ID # 12: security-related message - addressed
  • ID # 14: security-related message - to everyone
  • ID # 18: regular position report of a class B transceiver
  • ID # 21: Position and status report of an AtoN transceiver

Other telegram types:

  • ID # 24: Static ship data sent by class B, C, S tranceivers

In addition to the above-mentioned telegrams, other telegram types with an extended purpose (e.g. weather reports) can be defined internationally or regionally using the so-called "International Application Identifier" (IAI) or "Regional Application Identifier" (RAI). The standardized telegram of the binary message (binary message, ID # 6, # 8) is used as the container for the message content transmitted using this method.

Ship data

The AIS unit sends in the form of the above. Telegrams of ship-specific data that can be received and evaluated by any AIS receiver within range:

Static ship data
IMO number
Ship name
Callsign
MMSI number
Type of ship (freighter, tanker, tugboat, passenger ship, SAR , pleasure craft, etc.)
Dimensions of the ship (distance of the GPS antenna from the bow, stern, port and starboard sides)
Dynamic ship data
Navigational status (under engine, under sail, at anchor, moored, unable to maneuver, etc.)
Ship position (LAT, LON, in WGS 84 )
Ship position time (seconds only)
Course over ground (COG)
Speed ​​over ground (SOG)
Pre-alignment (HDG)
Course Change Rate (RED)
Travel data
current maximum static draft in dm
Dangerous goods class of the load (IMO)
Destination ( UN / LOCODE )
estimated time of arrival (ETA)

For inland AIS there is also:

ENI number
Association data (type ERI, length, width)
Dangerous goods class of the load
Draft in cm
Loading condition
Fairway side left / right (blue board)
Max. Height above water
Number of crew members
Number of passengers
Number of crew members

The navigational status and travel dates must be updated manually by the officer on watch . However, not all data have to be sent. Especially in the case of class B transmitters used in recreational shipping, often only the ship's name, MMSI, position, course and ship size are transmitted.

Sending the AIS data

The AIS signals are two FM - marine channels (.. AIS1 normally on and AIS2, i.e. VHF channel 87B and 88B with the frequencies 161.975  MHz and 162.025 MHz) with HDLC sent -Datenprotokoll in a fixed time frame. The data is decoded by appropriate software or end devices and z. B. graphically represented as text information or similar in a radar image .

The intervals at which a ship sends its data depend on the ship's speed and rate of change of course as well as on its maneuver status (underway, anchored or moored):

vehicle Send interval
Class A, at anchor or moored, not faster than 3 knots 3 min
Class A, at anchor or moored, faster than 3 knots 10 s
Class A, up to 14 kn 10 s
Class A, up to 14 kn when changing course 3 1 / 3 s
Class A, 14 to 23 kn 6 s
Class A, 14 to 23 kn when changing course 2 s
Class A, more than 23 kn 2 s
Class B, up to 2 kn 3 min
Class B, 2 to 14 kn 30 s
Class B, 14 to 23 kn 15 s (30 s with high frequency utilization)
Class B, more than 23 kn 5 s (15 s with high frequency utilization)

Use of AIS data on board

AIS screen

As explained in the “Delimitation” chapter, AIS is a data transmission system. A mandatory component of the AIS system on board is a so-called “Minimum Keyboard and Display” (MKD). The following explanations relate to the use of AIS data in the context of navigation systems such as B. in an ARPA system or in an electronic nautical chart (ECDIS) . These are not part of the actual AIS system.

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

The advantage of AIS compared to radar is, among other things, that the officer on watch knows the identity of other ships and changes in course and speed are automatically transmitted during maneuvers. This means that he can also make direct contact via marine radio and discuss necessary maneuvers.

With AIS, ship movements behind larger obstacles can also be recorded while sailing through the area; the radar is often overwhelmed in such situations because ships are not detected in the radar shadow. The VHF signals of the AIS reach these shadow areas much better due to the greater wavelength. On inland waterways , transceivers are set up in curves that are sealed off from radio signals, which transmit the AIS signals even over mountains.

The ship data can be integrated directly into the electronic nautical chart or processed by separate AIS software on the computer in order to display all ship movements, including one's own position. Separate software often offers a clearer representation, the display of additional data disseminated via AIS (in testing: weather reports, water levels) and better support in the event of a risk of collision.

Smaller marine vessels that do not require equipment can use the AIS data passively with inexpensive AIS receivers and display the position, course and speed of the surrounding equipped ships. The received data can be displayed on a small screen on the receiver, on an existing map plotter or with suitable software on a separate laptop / computer. In this way, you can initiate evasive maneuvers in good time if there is a risk of collision, especially when visibility is poor.

However, AIS cannot replace a radar system, as military vehicles, for example, often do not transmit AIS signals and many smaller vehicles are not equipped with an AIS transceiver . The transmitted data is also not always reliable.

Range

Ultra-short waves have a range that only slightly exceeds the geodetic visibility . This depends on the antenna height; one speaks here of quasi-optical signal propagation. For ship-to-ship connections, this is around 20 nautical miles (37 km). Coast stations receive signals from ships within a radius of 50–100 km, depending on the antenna height. AIS base stations are usually equipped with highly bundling antennas (directional characteristic) and are mounted higher than is possible on board, so that there are greater ranges.

Low-flying satellites can receive the VHF signals as long as the antennas are also directed upwards (omnidirectional). Orbcomm and Iridium equip their new satellites with AIS receivers. If the test is successful, the system could record all ships worldwide. Satellite-based AIS allows coastal states to monitor the waterways in regions that today do not by land-based VHF - Marine Radio to be covered.

In November 2009 , an AIS receiving antenna was installed on the European part of the ISS , the Columbus module . Since June 1, 2010, reception attempts with various AIS receivers have been carried out as part of an ESA study. Disturbing signal overlays due to the great distance of the radio horizon are countered with special signal processing techniques.

Airplane, navigation mark, land station

In addition to ships, the AIS also includes:

Short messages, traffic control

Short messages and free text messages ("safety related messages") specified by the IMO can also be transmitted via the AIS ; this telegram is internationally standardized (see "Telegrams" above). Via the IAI / RAI mechanism, z. For example, the automatic measuring stations broadcast current weather, water level and current data on navigation signs or route instructions are sent to ships. On rivers and canals, in particular in the area of ​​locks and bottlenecks, the AIS is increasingly used to direct traffic, for example to indicate the opening of the lock.

See also

Individual evidence

  1. Fischer Yvonne: Knowledge-based probabilistic modeling for situation analysis using the example of maritime surveillance . KIT Scientific Publishing, 2016, ISBN 978-3-7315-0460-3 ( google.de [accessed June 26, 2018]).
  2. Stefan Schultz, DER SPIEGEL: Illegal fishing: data analysis shows controversial reloading maneuvers on the high seas - DER SPIEGEL - Economy. Retrieved February 29, 2020 .
  3. Handbook inland shipping radio 2018. p. 4 , accessed on June 18, 2018 .
  4. boote-forum.de - The forum all about boats . ( boote-forum.de [accessed on May 7, 2017]).
  5. a b c d Internationale Fernmeldeunion : M.1371: Technical characteristics for an automatic identification system using time-division multiple access in the VHF maritime mobile band. February 2014, accessed December 27, 2018 .
  6. ^ Rheinschifffahrtspolizeiverordnung (PDF; 1.6 MB), §4.07 Inland AIS devices
  7. Inland AIS - Requirements and Options ( Memento of the original from January 21, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , WSV Bund - specialist center for traffic control technology  @1@ 2Template: Webachiv / IABot / www.ccr-zkr.org
  8. ↑ Transmission frequencies in the VHF range of the mobile maritime radio service and inland waterway radio service (PDF; 44 kB)
  9. IMO SN / Circ. 244 (pdf) IMO / BSH . 2005 week 31. Archived from the original on March 4, 2016. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved on August 23, 2009: "Guidance on the Use of the UN / LoCode in the Destination Field in AIS Messages" @1@ 2Template: Webachiv / IABot / www.bsh.de
  10. http://cdn2.hubspot.net/hubfs/183611/Collateral_for_Download/exactView_RT_Slick_Sheet.pdf
  11. Space Station keeps watch on world's sea traffic , ESA 2010
  12. ESA satellite receiver brings worldwide sea traffic tracking within reach , ESA 2009