10.3 Classes of AIS data
There are two classes of AIS data; each class supports a different range of AIS data.
AIS data is defined as Class A or Class B. The sending and receiving of Class A data is compulsory for larger vessels. You will therefore be able to view all larger vessels on your AIS display. Class B data is applicable to smaller vessels and is not compulsory. You should not therefore assume that your AIS is displaying all smaller vessels in your area.
Note: Not all AIS receivers will decode all information and not all of the Class A vessels input all of the required AIS data. For example, some inexpensive AIS Class B receivers do not decode and output information such as the ship’s name, IMO number and vessel draft/beam/length, destination and so on.
Your AIS receiver or transceiver may support additional AIS data that is not decoded by the multifunction display.
The following table lists the AIS information that is decoded by your multifunction display. (Y = Yes; N = No):
| Class A | Class B | Class B |
Data | (receive) | (send) | (receive) |
|
|
|
|
Ship’s name | Y | Y | Y |
|
|
|
|
Type | Y | Y | Y |
|
|
|
|
Call sign | Y | Y | Y |
|
|
|
|
IMO number | Y | N | N |
|
|
|
|
Length and beam | Y | Y | Y |
|
|
|
|
Antenna location | Y | Y | Y |
|
|
|
|
| Class A | Class B | Class B |
Data | (receive) | (send) | (receive) |
Draft | Y | N | N |
|
|
|
|
Cargo | Y | Y | Y |
Information |
|
|
|
Destination | Y | N | N |
|
|
|
|
ETA | Y | N | N |
|
|
|
|
Time | Y | Y | Y |
|
|
|
|
Ship’s position | Y | Y | Y |
|
|
|
|
COG | Y | Y | Y |
|
|
|
|
SOG | Y | Y | Y |
|
|
|
|
Gyro heading | Y | Y | Y |
|
|
|
|
Rate of turn | Y | N | N |
|
|
|
|
Navigational | Y | N | N |
status |
|
|
|
Safety message | Y | N | Y |
|
|
|
|
136 |
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