Group assignment command

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msg_ID: 
23
Extended description: 
Assignment of a specific report behaviour by competent authority using a Base station to a specific group of mobiles
Priority: 
1
Access scheme: 
FATDMA
RATDMA
Communication state: 
N/A
Transmitted by: 
Base station

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

ParameterNumber of bitsDescription
Message ID6Identifier for Message 23; always 23
Repeat indicator2Used by the repeater to indicate how many times a message has been repeated.
0-3; default = 0; 3 = do not repeat any more
Source ID30MMSI of assigning station
Spare2Spare. Should be set to zero
Longitude 118Longitude of area to which the group assignment applies; upper right corner (north-east); in 1/10 min
(±180°, East = positive, West = negative)
Latitude 117Latitude of area to which the group assignment applies; upper right corner (north‑east); in 1/10 min
(±90°, North = positive, South = negative)
Longitude 218Longitude of area to which the group assignment applies; lower left corner (south-west); in 1/10 min
(±180°, East = positive, West = negative)
Latitude 217Latitude of area to which the group assignment applies; lower left corner (south‑west); in 1/10 min
(±90°, North = positive, South = negative)
Station type40 = 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 type80 = all types (default)
1...99 see Table 53
100...199 reserved for regional use
200...255 reserved for future use
Spare22Not used. Should be set to zero. Reserved for future use
Tx/Rx mode2This 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 interval4This parameter commands the respective stations to the reporting interval given in Table 77
Quiet time40 = default = no quiet time commanded; 1-15 = quiet time of 1 to 15 min
Spare6Not used. Should be set to zero. Reserved for future use
Number of bits160Occupies 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 settingReporting interval for Message 23
0As given by the autonomous mode
110 min
26 min
33 min
41 min
530 s
615 s
710 s
85 s
9Next shorter reporting interval
(only applicable if in autonomous mode)
10Next longer reporting interval
(only applicable if in autonomous mode)
112 s (not applicable to the Class B “CS” and Class B “SO”)
12-15Reserved 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.