6.Regional Assignment Channel Assignment Message (NMEA 0183 ACA)
ANauticast™-B unit can receive regional channel management information in two ways: ITU-R M.1371 message 22 or a DSC telecommand received on channel 70. Channel management information is applied based upon the actual location of the AIS device. An AIS unit is “using” channel management information when the information is being used to manage the operation of the VHF receiver and/or transmitter inside the AIS unit. This sentence is used both to enter and obtain channel management information. When sent to an AIS unit, the ACA sentence provides regional information that the unit stores and uses to manage the internal VHF radio. When sent from an AIS unit, the ACA sentence provides the current channel management information retained by the AIS unit. The information contained in this sentence is similar to the information contained in an ITU-R M.1371-1 message 22. The information contained in this sentence directly relates to the Initialization Phase and Dual Channel Operation and Channel Management functions of the AIS unit as described in ITU-R M. 1371.
ACA message format
$--ACA,x,llll.ll,a,yyyyy.yy,a,llll.ll,a,yyyyy.yy,a,x,xxxx,x,xxxx,x,x,x,a,x,hhmmss.ss field 1 2 3 4 5 6 7 8 91011121314 15
| Field | | | Format | | | Description | |
| | | | | |
1 | | x | | | Sequence Number , 0 to 9 | |
2 | | IIII, II, a | | | Region Northeast corner latitude – N/S | |
3 | | yyyyy.yy,a | | | Region Northeast corner longitude – E/W | |
4 | | IIII, II, a | | | Region Southwest corner latitude – N/S | |
5 | | yyyyy.yy,a | | | Region Southwest corner longitude – E/W | |
6 | | x | | | Transition Zone Size | |
7 | | xxxx | | | Channel A | |
8 | | x | | | Channel A bandwidth | |
9 | | xxxx | | | Channel B | |
10 | | x | | | Channel B bandwidth | |
11 | | x | | | Tx/Rx mode contro | |
12 | | x | | | Power level control | |
13 | | a | | | Information source | |
14 | | x | | | In-Use Flag | |
15 | | hhmmss.ss | | | Time of "in-use" change | |
7.Channel management information source messages (NMEA 0183 ACS)
This sentence is used in conjunction with the ACA sentence. This sentence identifies the originator of the information contained in the ACA sentence and the date and time the AIS unit received that information.
ACS message format
!-- ACS,x,xxxxxxxxx, hhmmss.ss,xx,xx,xxxx*hh<CR><LF> field 1 2 3 4 5 6
| Field | | | Format | | | Description | |
| | | | | |
1 | | x | | | Sequence Number , 0 to 9 | |
2 | | xxxxxxxxx | | | MMSI of originator | |
3 | | hhmmss.ss | | | UTC of receipt of channel management information | |
4 | | xx | | | UTC Day, 01 -31 | |
5 | | xx | | | UTC Month, 01 -12 | |
6 | | xxxx | | | UTC Year | |
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Y1-03-0222 Rev. C
