Text description
14.1 This message provides a text description in combination with other AIS Application-Specific Message.
14.2 This message can be broadcast or addressed, but must be the same as the main message that it is linked to.
14.3 The Message Linkage ID is used to link the Text Description message to another AIS Application-Specific Message (e.g., Area Notice or Route Information). The same source MMSI must be used to send both the main message and Text Description message.
14.4 Up to 5-slot messages can be created, however messages greater than 3 slots should be avoided.
Table 14.3
Text description – (broadcast)
| Parameter | No of bits |
Description |
|---|---|---|
| Message ID | 6 | Identifier for Message 8; always 8. |
| Repeat Indicator | 2 | Used by the repeater to indicate how many times a message has been repeated.
0 – 3 0 = default 3 = do not repeat anymore |
| Source ID | 30 | MMSI number of source station. |
| Sequence Number | 2 | 0 – 3; refer to § 5.3.1, Annex 2 of ITU-R M.1371-3. |
| Destination ID | 30 | MMSI number of destination station. |
| Retransmit Flag | 1 | Retransmit Flag should be set upon retransmission.
0 = no retransmission = default 1 = retransmitted |
| Spare | 1 | Not used. Set to zero. |
| IAI | 16 | DAC = 001; FI = 29
(See Rec. ITU-R M.1371-3, Annex 5, § 2.1. |
| Message Linkage ID | 10 | Used to link the Text Description message with a main message. The Connection ID and source MMSI MID uniquely identifies the main message.
1 – 1,023 0 = not available = default |
| Text String | 6 – 966 | Free text 1 – 155 characters 6-bits ASCII). If applicable, recommended to use IMO Standard Marine Communication Phrase (SMCP) (see IMO A.918(22)). Number of slots used should be minimized, refer to Table 14.4. |
| Spare | 0 | Not used. Set to zero. |
| Total | 72 – 1032 | Occupies 1 – 5 slots (see Table 14.4). |
Number of slots if sent as an addressed message
| Number of characters in the message | 1-6 | 7-43 | 44-81 | 82-118 | 119-155 |
| Number of slots used | 1 | 2 | 3 | 4 | 5 |