14.4 Functional Supplement to Global Satellite Radio Navigation Systems
273
The AIS station is connected to external ship equipment. Typically, the following
systems are used as external equipment:
• sources of navigation data (receiver of the global navigation satellite system
(GNSS), log, compass or its integrating device);
• electronic navigation devices capable of displaying and processing data issued by
the AIS station: ECDIS, ARPS, pilot AIS.
Ships equipped with AIS equipment, while on the high seas or in coastal areas,
regularly transmit standard messages in the VHF (ultra-short waves) range of the
maritime mobile radio service containing static, dynamic and voyage information on
the vessel. Simultaneously, each vessel equipped with AIS receives similar information from other vessels within the range limited by the propagation of VHF
radio waves (20–30 miles). The received information is automatically processed
and displayed on one of the ship’s navigation displays. Synchronization of operation
of all AIS stations (ship and coastal) is provided by GNSS, which is also a source of
transmitted information on coordinates and velocity vector. In coastal areas where
AIS base stations are installed, information transmitted by ships is received by base
stations and enters the disposal of coastal services (VTS and ship reporting systems,
search and rescue services, environmental control and pollution elimination services,
border and customs authorities, various port services). Usually, to obtain a complete
picture of shipping in a controlled area, AIS base stations are combined into networks
that allow integrating information from remote base stations with each other, as well
as with information received in the VTS and in mandatory ship reporting systems. In
coastal areas, the accuracy of GNSS positioning of vessels, and therefore the effectiveness of AIS, can be improved by coastal reference stations and radio beacons that
transmit differential corrections to vessels. AIS base (coastal) stations can operate in
an active mode, controlling the mode of operation of ship stations and transmitting
information related to the safety of navigation (local navigation warnings, differential
corrections for GNSS, data on vessels maintained by a VTS).
The display of the received and processed information is carried out on the screen
of the ship navigation graphic display (ARPS, electronic cartographic system, integrated navigation system). The result is a visual representation of the situation, much
like an ARPS screen.
Despite the fact that one of the main sources of navigational information, both
for ships and for coastal services, is a radar locator, under certain conditions of use
it has a number of disadvantages:
• short detection range of targets, especially small ones in sizes;
• strong influence of interference from the sea or atmospheric phenomena;
• insufficient resolution capability;
• limitations due to the peculiarities of the beams passage (the target is not visible
behind obstacles);
• the use of filtering algorithms makes it difficult to discriminate target maneuvers;
• transfer of markers of tracked target vessels (swopping) when they approach,
during ARPS operation.
273
The AIS station is connected to external ship equipment. Typically, the following
systems are used as external equipment:
• sources of navigation data (receiver of the global navigation satellite system
(GNSS), log, compass or its integrating device);
• electronic navigation devices capable of displaying and processing data issued by
the AIS station: ECDIS, ARPS, pilot AIS.
Ships equipped with AIS equipment, while on the high seas or in coastal areas,
regularly transmit standard messages in the VHF (ultra-short waves) range of the
maritime mobile radio service containing static, dynamic and voyage information on
the vessel. Simultaneously, each vessel equipped with AIS receives similar information from other vessels within the range limited by the propagation of VHF
radio waves (20–30 miles). The received information is automatically processed
and displayed on one of the ship’s navigation displays. Synchronization of operation
of all AIS stations (ship and coastal) is provided by GNSS, which is also a source of
transmitted information on coordinates and velocity vector. In coastal areas where
AIS base stations are installed, information transmitted by ships is received by base
stations and enters the disposal of coastal services (VTS and ship reporting systems,
search and rescue services, environmental control and pollution elimination services,
border and customs authorities, various port services). Usually, to obtain a complete
picture of shipping in a controlled area, AIS base stations are combined into networks
that allow integrating information from remote base stations with each other, as well
as with information received in the VTS and in mandatory ship reporting systems. In
coastal areas, the accuracy of GNSS positioning of vessels, and therefore the effectiveness of AIS, can be improved by coastal reference stations and radio beacons that
transmit differential corrections to vessels. AIS base (coastal) stations can operate in
an active mode, controlling the mode of operation of ship stations and transmitting
information related to the safety of navigation (local navigation warnings, differential
corrections for GNSS, data on vessels maintained by a VTS).
The display of the received and processed information is carried out on the screen
of the ship navigation graphic display (ARPS, electronic cartographic system, integrated navigation system). The result is a visual representation of the situation, much
like an ARPS screen.
Despite the fact that one of the main sources of navigational information, both
for ships and for coastal services, is a radar locator, under certain conditions of use
it has a number of disadvantages:
• short detection range of targets, especially small ones in sizes;
• strong influence of interference from the sea or atmospheric phenomena;
• insufficient resolution capability;
• limitations due to the peculiarities of the beams passage (the target is not visible
behind obstacles);
• the use of filtering algorithms makes it difficult to discriminate target maneuvers;
• transfer of markers of tracked target vessels (swopping) when they approach,
during ARPS operation.