Theo Quy định 19 đoạn 2.4 Chương V của SOLAS 1974 (IMO), đã sửa đổi, yêu cầu tất cả các tàu có tổng dung tích 300 trở lên chạy tuyến quốc tế, tất cả tàu hàng có tổng dung tích 500 trở lên chạy tuyến quốc tế và tất cả các tàu khách không kể kích thước phải lắp đặt hệ thống nhận dạng tự động (AIS). IMO cũng đã đưa ra khuyến cáo về một lộ trình lắp đặt AIS trên các tàu chỉ định từ nay đến 2008. Đến nay đã có nhiều tàu lắp đặt thiết bị AIS.
Trang 1Automatic Identification System AIS
The AIS transponder is an onboard system operating in the
VHF marine band, capable to transmit ship’s information
such as ID, position, course, direction, origin, vessel type,
draft, freight (especially if dangerous), etc.
AIS
Trang 2The collection of cinematic data of the vessel is mainly based on the navigation control
by satellite global positioning systems (e.g GPS / DGPS), suitable both in narrow
waterways and in open sea
This technology allows the automatic position dispatch of the position and of the other information relevant to the vessel in a reliable way and with affordable costs, joining a GPS receiver unit and a VHF radio transceiver operating within the band assigned to AIS systems and compliant with the ITU-RM.1371 recommendation
These devices are both included in the AIS transponder which, with reference to Fig 1, fully performs the function of data collection through GPS, communication through VHF radio and data distribution to the external presentation units, both local and remote The system can forward up to 2000 reports per minute and update them every 2
seconds, and exploits the “Self-Organizing Time Division Multiple Access” (SOTDMA) technology to allow high data exchange rate and ensure ship-to-ship operation
The system is also compatible with the “Digital Selective Calling Systems”, thus allowing
to the land based GMDSS (Global Maritime Distress and Safety System) to establish in a cheap way the operation of the AIS channel and to identify and track the vessels
equipped with the transponder
Operation mode
The main information, like position and speed, is normally provided by the Global
Positioning System (GPS, optionally DGPS)
The other information, such as direction, SOG (Speed Over Ground), Rate of Turn, Angle
of Heel, roll and pitch, destination and ETA (Estimated Time of Arrival), can be provided
by the sensors onboard the vessels themselves
The AIS transponder normally works in an autonomous and continuous way, regardless
if it is installed in open sea, on the coastline or in the hinterland
The used frequencies, 9.6 Kb GMS in FM with channels spacing 12.5 KHz or 25 KHz, are prescribed by the ITU-R 1084-2 recommendation and use an HDLC protocol
Though only one channel is strictly necessary, each station transmits and receives on several channels in order to avoid interference problems and allow the channels to be reallocated without losing the connection with the other vessels
The AIS provides for the resolution of the problems due to the conflict of two or more connections, thus preserving the integrity of the communication also in overload
conditions
Every station sets its transmission slot based on the traffic chronology and on the
knowledge about the future actions of the various stations
A position report of an AIS station occupies one over 2250 transmission slots every 60 seconds The AIS stations are constantly synchronized with each-other and avoid the overlapping of the slots; the selection of the transmission slots by each station is random within a defined time span
It is also possible to send text messages both ship-to-ship and ship-to-shore
The operator composes a text message, inclusive of the addressee; the AIS transponder recognizes the dispatch request and puts the message in the suitable format for the following transmission All the ships within the area controlled by a shore station of the AIS will be able to exchange messages
The AIS transponder decides automatically when to send the text message
Trang 3As an information system, the AIS can be
split into 3 basic activities:
- information collection
- information transmission
- information presentation
T he mai n el ements i ncl uded i n the information, as for example:
- ship’s name
- ship’s position
- ship’s course
- ship’s speed
It is straightforward to integrate the AIS technology in a VTS (Vessel Traffic System) or in its more complex version VTMIS (Vessel Traffic Management and Information System)
An AIS-based VTS allows to
c o n s i d e r a b l y e n h a n c e t h e
p e r f o r m a n c e i n t e r m s o f awareness of the situation being and data processing, with great advantage for the activities of
d e c i s i o n - m a k i n g f o r t h e assistance to the sailors during navigation
The contribution of the AIS to the VTS is sketched in Fig 2
are gathered from the onboard
s e n s o r s , f o r w a r d e d a n d
displayed on the desired device
(ARPA radar, laptop PC with
charting facility, IMO compliant
ECDIS system, etc.), according
to the user requirement
Data presentation on
an “ad hoc” device Ship’s cinematic data collection and
translation in the AIS sentence format
Initialization and control of the data flow of the AIS sentences among the participant units (ship-to-ship, ship-to-shore)
Fig 1 shows the basic elements
of the AIS
Fig 1
ForewordWithin the scope of the management and control of the maritime traffic from land control centers for accident prevention and navigation safety it’s today growing the demand for technically advanced devices, to provide always better performances in terms of navigation prediction (both onboard and in the shore control sites) and capability and speed in the information distribution
Considering that the management of the operations at sea is also influenced by the local situation and by the risks involved in the marine activities at whatever level, the AIS system stands as a technologically advanced tool for the safety of the life at sea and for the control
of vessel traffic, in full cooperation / integration with the traditional devices such as video / audio radiocommunication as well as with the most advanced systems such as VTMIS (Vessel Traffic Management and Information System), allowing a complete and detailed view
of the overall situation within a wide area under surveillance
As a matter of fact, under the acronym “AIS” is more correctly included the whole set of processors, equipment, facilities, personnel, software and procedures cooperating in order to classify, organize, evaluate, process, compact, store and retrieve data and information relevant to the navigation and annexed activities, with the human intervention reduced to a minimum
The AIS is an efficient tool to exchange the positioning data among the participant naval units and the land control centers and represent them on a suitable display; it has the value
to enhance the level of navigation safety for all the involved vessels, providing an adequate coverage also beyond the VTS range, allowing the radio bidirectional communication both in the ship-to-ship and ship-to-shore mode
Fig 2
Trang 4This brochure should not be sell The specifications given herein may be changed by the manufacturer, GEM Elettronica S.r.l., at any time without notice Registrazione N 022A
ISO 9001 Certification Number 120
Via A.Vespucci, 9 63039 S.Benedetto del Tronto (AP) - I T A L Y
Tel +39 0735 - 59051 - Telefax +39 0735 - 590540
®
Type of ship Tonnage Voyage Date
All new-build ships >300 International 2002 New cargo ships >500 Non-international 2002 New passenger ships ALL International 2002 Existing passenger ships ALL International 2003 Existing tankers ALL International 2003 Existing ships >50000 International 2004 Existing ships 10000 to 50000 International 2005 Existing ships 3000 to 10000 International 2006 Existing ships 300 to 3000 International 2007 Existing ships ALL Non-international 2008
Installation of the AIS transponder
General specifications:
Power consumption: 75W Power supply requirements: 24 VDC -10% +30%
Default frequencies:
AIS1 161.975 MHZ AIS2 162.025 MHZ DSC channel 70: 156.525 MHz Operating temperature: from -15 °C to +55 °C Storage temperature: from -20 °C to +70 °C Environmental conditions: as per IEC 60945 Built-in GNSS: Optional GLONASS/GPS
AIS/DSC Transmitter:
Power output: 12.5 W or 2.0 W Frequency range: 156.025 - 162.025 MHz Antenna output impedance: 50 Ω
TDMA Receivers:
Sensitivity: (PER) < 10% at -107 dBm (25kHz) Frequency range: 156.025 - 162.025 MHz
Channel spacing: 12.5 or 25 kHz Modulation: GMSK Data rate: 9,600 bits/s Frequency stability: < ± 1ppm
DSC Receiver:
Sensitivity: BER <10-4 at 107 dBm Frequency range: 155.3 - 162.5 MHz Channel spacing 25kHz
Modulation 1300Hz/2100Hz - FSK Frequency stability < ± 1ppm
Transmitted information:
e-mail: marketing@gemrad.com; internet: www.gemrad.com
According to the IMO requirements for AIS, the transponder is or will become mandatory onboard the following vessels
Static
- IMO number
- Caller identification and name
- Length and orientation
- Type of ship
- Antenna location onboard (bow or aft)
Dynamic
- E x a c t s h i p ’ s p o s i t i o n a n d s t a t u s
integrity
- UTC time
- Course over ground (COG)
- Speed over ground (SOG)
- Direction
- Rate of turn
- Optional – roll and pitch (field not
included in the basic message)
- O p t i o n a l – y a w a n g l e ( f i e l d n o t
included in the basic message)
- Navigation status (e.g.: Not Under
C o m m a n d ( N U C ) , a t a n c h o r , e t c –
manual input)
- Other information from external ship’s
sensors can be added navigation or
meteorological conditions