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AIS PRODUCTS DESCRIPTION

1.1   AYSTEM OVERVIEW

AIS is one of the latest AtoN equipments allowing real-time information exchanged between Vessels and Traffic Service system.

   

    AIS uses marine VHF channel with frequency set universally from 156.025MHz to 162.025MHz. AIS applies the broadcast method of time division multiple access (hereinafter called “TDMA”) TO transmit in a 2250 messages per minute rate. The whole broadcasting process does not require manual operating and it automatically generates networks so vessels can be easily identified with each other.

 



   
 AIS system is capable of integrating and combining with other maritime system such as Electronic Chart System (hereinafter called “ECS”). AIS’ wide applications and its exception AtoN value greatly enhance other maritime systems’ performance.

     Having an AIS system on board not only can monitor the status of the vessels in the surrounding sea, but also to receive the dynamic information (position, speed, SOG, and etc),

Static information, and voyage related information from any vessels equipped with an AIS system.

 

1.2. AIS COVERAGE

  The system radio coverage will be similar to other VHF radio applied products. However,

How far the AIS system can transmit will also depends on the length of its external Antenna and the earth’s curvature. The longer of the antenna, and the higher it is set, will have slight difference in how far signal will transmit. Generally, the AIS signal coverage will be around 25 nautical miles.

 

1.3. AIS V.S. RADAR

  Each AIS equipped vessel automatically broadcasts its own vessel information and will not encounter signal blocked out by capes or islands. AIS system also updates and broadcasts its speed, voyage related information and etc constantly. Comparing with Radar system, AIS system is much more effective in showing a vessel’s real-time voyage status and to provide collision avoidance warming beforehand.

 

  AIS system is primarily designed for the purpose of collision avoidance. It greatly enhances the add-on value of other maritime system such as the ARPA Radar, VTS, and etc. An AIS-integrated ECS system can easily plot all vessels’ information, such as vessels’ names, position, headings, and etc on its plotter.

 

1.4. TYPE OF AIS

 While there are Class A, Class B, and Receiver type AIS, their intended nature to navigate are different.

Table 1-1 Type of AIS

Class A AIS

·Transmits and receives AIS signal.

·Intended for vessels meeting the requirements of IMO AIS carriage requirements.

·The Class A AIS is mandated to be installed on all commercial vessels exceed 300 tons.

Class B AIS

·Transmits and receives AIS signal.

·Not necessarily in full accord with IMO AIS carriage requirements.

·The Class B AIS currently is not mandated to be installed on any vessels.

·Suitable for recreational purpose enhancing the safety at sea.

Receiver Type AIS

·Only receives AIS signal.

·Does not have transmitter to send out AIS signal.

·Suitable for recreational vessel that does not want to send out its vessel information.

 

1.5. AIS DATA INFORMATION

In the following table, some data details are lighted I black and these data are mandated, by law, to be transmitted and received from Class A AIS equipped vessels only.

 

Table 1-2 AIS data information

Type of Data

Data Details

Static Data

Maritime Mobile Service Identity (hereinafter called “MMSI”) number

IMO number

Called sign and name

Type of ship

Length and beam

GPS Antenna location

Voyage Related Data

Drought of the ship

Cargo information

Destination

Estimate Time of Arrival (hereinafter called “ETA”)

Dynamic Data

Position of the vessel

Coordinated Universal Time (hereinafter called “UTC”)

Course Over Ground (hereinafter called “COG”)

Speed Over Ground (hereinafter called “SOG”)

Heading

Rate of turn

Navigational status

Dynamic Reports

Speed of the ship

Status of the ship

SRM

Alarm

Safety

 

1.6. AIS REPORT RATE

A Class B AIS has two different data report rates. One report rate is in accordance to ITU-RM. 1371 standard with SOTDMA broadcasting method. The other is in accordance to IEC62287 standard with CSTDMA broadcasting method. For details please refer to the following tables.

 

SOTDMA Broadcasting Method:


Table 1-3-1 AIS report rate

Platform Condition

Nominal Reporting Interval

Class B Ship-borne mobile equipment not moving faster than 2 knots

3 Minutes

Class B Ship-borne mobile equipment moving 2-14 knots

30 Seconds

Class B Ship-borne mobile equipment moving 14-23 knots

15 Seconds

Class B Ship-borne mobile equipment moving faster than 23 knots

5 Seconds

Search and Rescue aircraft (aisborne mobile equipment)

10 Seconds

Aids to Navigation

3 Minutes

AIS base station

10 Seconds

 

AIS is with CSTDMA Broadcasting Method as follows:

 

Picture 1-3-2 AIS report rate

Platforms Condition

Nominal

Reporting Interval

Class B Ship-borne mobile equipment not moving faster than 2 knots

3 Minutes

Class B Ship-borne mobile equipment moving faster than 2 knots

30 Seconds

Report rate command of VTS

5 Seconds highest

 



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