The Group assignment command is transmitted by a base station when operating as a controlling entity(see § 4.3.3.3.2 Annex 7 and § 3.20). This message should be applied to a mobile station within the defined region and as selected by “Ship and Cargo Type” or “Station type”. The receiving station should consider all selector fields concurrently. It controls the following operating parameters of a mobile station:
– transmit/receive mode;
– reporting interval;
– the duration of a quiet time.
Station type 10 should be used to define the base station coverage area for control of Message 27 transmissions by Class A and Class B “SO” mobile stations. When station type is 10 only the fields latitude, longitude are used, all other fields should be ignored. This information will be relevant until three minutes after the last reception of controlling Message 4 from the same base station (same MMSI).
TABLE 76
Parameter | Number of bits | Description |
Message ID | 6 | Identifier for Message 23; always 23 |
Repeat indicator | 2 | Used by the repeater to indicate how many times a message has been repeated. 0-3; default = 0; 3 = do not repeat any more |
Source ID | 30 | MMSI of assigning station |
Spare | 2 | Spare. Should be set to zero |
Longitude 1 | 18 | Longitude of area to which the group assignment applies; upper right corner (north-east); in 1/10 min (±180°, East = positive, West = negative) |
Latitude 1 | 17 | Latitude of area to which the group assignment applies; upper right corner (north‑east); in 1/10 min (±90°, North = positive, South = negative) |
Longitude 2 | 18 | Longitude of area to which the group assignment applies; lower left corner (south-west); in 1/10 min (±180°, East = positive, West = negative) |
Latitude 2 | 17 | Latitude of area to which the group assignment applies; lower left corner (south‑west); in 1/10 min (±90°, North = positive, South = negative) |
Station type | 4 | 0 = all types of mobiles (default); 1 = Class A mobile stations only; 2 = all types of Class B mobile stations; 3 = SAR airborne mobile station; 4 = Class B “SO” mobile stations only; 5 = Class B “CS” shipborne mobile station only; 6 = inland waterways; 7 to 9 = regional use; 10 = base station coverage area (see Message 4 and Message 27); 11 to 15 = for future use |
Type of ship and cargo type | 8 | 0 = all types (default) 1...99 see Table 53 100...199 reserved for regional use 200...255 reserved for future use |
Spare | 22 | Not used. Should be set to zero. Reserved for future use |
Tx/Rx mode | 2 | This parameter commands the respective stations to one of the following modes: 0 = TxA/TxB, RxA/RxB (default); 1 = TxA, RxA/RxB, 2 = TxB, RxA/RxB, 3 = reserved for future use |
Reporting interval | 4 | This parameter commands the respective stations to the reporting interval given in Table 77 |
Quiet time | 4 | 0 = default = no quiet time commanded; 1-15 = quiet time of 1 to 15 min |
Spare | 6 | Not used. Should be set to zero. Reserved for future use |
Number of bits | 160 | Occupies one-time period |
TABLE 53
Identifiers to be used by ships to report their type | ||||
Identifier No. | Special craft | |||
50 | Pilot vessel | |||
51 | Search and rescue vessels | |||
52 | Tugs | |||
53 | Port tenders | |||
54 | Vessels with anti-pollution facilities or equipment | |||
55 | Law enforcement vessels | |||
56 | Spare – for assignments to local vessels | |||
57 | Spare – for assignments to local vessels | |||
58 | Medical transports (as defined in the 1949 Geneva Conventions and Additional Protocols) | |||
59 | Ships and aircraft of States not parties to an armed conflict | |||
Other ships | ||||
First digit(1) | Second digit(1) | First digit(1) | Second digit(1) | |
1 – Reserved for future use | 0 – All ships of this type | – | 0 – Fishing | |
2 – WIG | 1 – Carrying DG, HS, or MP, IMO hazard or pollutant category X(2) | – | 1 – Towing | |
3 – See right column | 2 – Carrying DG, HS, or MP, IMO hazard or pollutant category Y(2) | 3 – Vessel | 2 – Towing and length of the tow exceeds 200 m or breadth exceeds 25 m | |
4 – HSC | 3 – Carrying DG, HS, or MP, IMO hazard or pollutant category Z(2) | – | 3 – Engaged in dredging or underwater operations | |
5 – See above | 4 – Carrying DG, HS, or MP, IMO hazard or pollutant category OS(2) | – | 4 – Engaged in diving operations | |
| 5 – Reserved for future use | – | 5 – Engaged in military operations | |
6 – Passenger ships | 6 – Reserved for future use | – | 6 – Sailing | |
7 – Cargo ships | 7 – Reserved for future use | – | 7 – Pleasure craft | |
8 – Tanker(s) | 8 – Reserved for future use | – | 8 – Reserved for future use | |
9 – Other types of ship | 9 – No additional information | – | 9 – Reserved for future use | |
DG: dangerous goods HS: harmful substances MP: marine pollutants (1) The identifier should be constructed by selecting the appropriate first and second digits. (2) NOTE 1 – The digits 1, 2, 3 and 4 reflecting categories X, Y, Z and OS formerly were categories A, B, C and D. |
TABLE 77
Reporting interval settings for use with message 23
Reporting interval field setting | Reporting interval for Message 23 |
0 | As given by the autonomous mode |
1 | 10 min |
2 | 6 min |
3 | 3 min |
4 | 1 min |
5 | 30 s |
6 | 15 s |
7 | 10 s |
8 | 5 s |
9 | Next shorter reporting interval (only applicable if in autonomous mode) |
10 | Next longer reporting interval (only applicable if in autonomous mode) |
11 | 2 s (not applicable to the Class B “CS” and Class B “SO”) |
12-15 | Reserved for future use |
NOTE 1 – When the dual channel transmission is suspended by Tx/Rx mode command 1 or 2, the required reporting interval should be maintained using the remaining transmission channel. |