Target of Interest (encrypted)
The Target of Interest message is used to report contacts.
Usage Notes
- The Message 26 TOI Message format provides for both a broadcast and addressed TOI message variation. Addressing, when required, shall be performed using the Destination Indicator and Destination ID fields inherent to the Message 26 structure.
- The report is intended to be repeated every 15 seconds until cancelled locally. The PI shall not retransmit if an ACK is not received.
- Cancelling a TOI locally stops transmission of TOI message repetitions.
- Remote units receiving a TOI will apply Lost Target/Auto Drop processing rules to remove the TOI designation from a target.
- Cancellation messages repeat four (4) times, 15 seconds apart. The PI shall not retransmit the cancellation message if an ACK is not received.
- This message can be used to report either vessel or aircraft targets.
Encrypted Target of Interest (Message 26, Addressed)
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Parameter |
# of Bits |
Description |
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Standard Message Header |
Message ID |
6 |
Identifier for Message 26; always 26. |
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Repeat Indicator |
2 |
Indicates how many times a message has been repeated. 0 – 3; 0 = default; 3 = do not repeat any more. Set to zero (default). |
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Source MMSI |
30 |
MMSI number of source station. Varies according to the transmitter ID. |
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Destination Indicator |
1 |
0 = broadcast (no Destination ID field) 1 = Addressed (30 bit Destination ID field). Set to 1 (addressed). |
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Binary Data Flag |
1 |
0 = unstructured binary data (no Application Identifier bits used) 1 = binary data coded as defined by the 16-bit AI. Set to 1 (structured). |
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Destination ID |
30 |
MMSI number of destination station. |
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Spare |
2 |
Not used, Set to zero. |
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Designated Area Code |
10 |
Designated area code (DAC). Set to 366. |
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Function Identifier |
6 |
Function identifier. Set to 18. |
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Encrypted Payload |
Version |
3 |
Sequential number used to indicate the message version in steps of 1. 0 = test message = default; 1 – 7 = message version. Set to zero. |
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Message Linkage ID |
10 |
A source-specific random number, unique across recent binary messages with Message Linkage ID. Used to connect the additional information in this Text Message with another ASM. The Message Linkage ID and the source MMSI uniquely identify the sent message. 1 – 1023; 0 = not available. |
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Target Acquisition Source |
3 |
Type of Target. 0 = unknown = default; 1 = AIS, 2 = Radar, 3 = visual sighting; 4 = reported; 5 = other electronic surveillance, i.e. DSC, ECDIS, etc.; 6 -7 = reserved. |
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Target ID |
30 |
MMSI if type is Target Acquisition source=1 (AIS), Sender generated ID otherwise |
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TOI Status |
2 |
Designator for TOI Status 0 = cancel; 1 = active; 2 = being followed; 3 = being boarded. |
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Target Type |
3 |
Type of Target 0 = vessel = default; 1 = aircraft; 2 = submersible; 3-7 = reserved. |
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Target Description and Cargo |
8 |
Description of target type and cargo, see Appendix 3. |
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Interest |
8 |
Code to indicate what interest in vessel is. To be defined. Could be used as an 8- bit binary matrix, similar to ATON Status bits. TBD. |
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Time of TOI Report |
UTC Hour |
5 |
UTC Hour of TOI report. 0 – 23; 24 = UTC hour not available = default; 25 - 31 = reserved. |
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UTC Min |
6 |
UTC Minute of TOI report. 0 – 59; 60 = UTC minute not available = default; 61 - 63 (reserved for future use). |
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UTC Sec |
6 |
UTC Second of TOI report. 0 – 59; 60 = UTC second not available = default; 61 - 63 (reserved). |
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Longitude |
28 |
Longitude in 1/10,000 min (+/-180 degrees, East = positive, West = negative - 2’s complement). 181 degrees = not available = default. |
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Latitude |
27 |
Latitude in 1/10,000 min (+/-180 degrees, East = positive, West = negative - 2’s complement). 91 degrees = not available = default. |
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SOG |
10 |
Speed over ground. Scale dependent on value of craft flag. Aircraft: 0 – 1000 kts (1 kt increments); 1001 = 1001 kts or higher; 1002 = not available = default; 1003 – 1023 = reserved. Vessel: 0 – 100.0 kts (0.1 kt increments); 1001 = 100.1 kts or higher; 1002 = not available = default; 1003 – 1023 = reserved. |
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COG |
12 |
Course over ground in 1/10 degree steps. 0 - 359.9 degrees; 3600 = not available = default; 3601 - 4095 = reserved. |
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Encryption Bit Padding |
95 |
Sufficient spare bits to ensure that the binary data is a multiple of 128 bits for block encryption (256). Set to zero. |
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Checksum |
16 |
16-bit CRC calculated as per EAIS Specification |
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Footer |
Spare |
4 |
Four extra bits to ensure the message ends on a byte boundary. Set to zero. |
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Communications State Selector |
1 |
0 = SOTDMA communication state follows 1 = ITDMA communication state follows |
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Communications State |
19 |
SOTDMA communication state (see ITU 1371-5 § 3.3.7.2.1, Annex 2), if communication state selector flag is set to 0, or ITDMA communication state (§ 3.3.7.3.2, Annex 2), if communication state selector flag is set to 1. |
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Total bits |
384 |
2 Slot Binary Message |
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- Message 26 Broadcast Format
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Encrypted Target of Interest Message (Message 26, Broadcast)
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Parameter |
# of Bits |
Description |
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Standard Message Header |
Message ID |
6 |
Identifier for Message 26; always 26. |
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Repeat Indicator |
2 |
Indicates how many times a message has been repeated. 0 – 3; 0 = default; 3 = do not repeat any more. Set to zero (default). |
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Source MMSI |
30 |
MMSI number of source station. Varies according to the transmitter ID. |
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Destination Indicator |
1 |
0 = broadcast (no Destination ID field) 1 = Addressed (30 bit Destination ID field). Set to zero (broadcast). |
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Binary Data Flag |
1 |
0 = unstructured binary data (no Application Identifier bits used) 1 = binary data coded as defined by the 16-bit AI. Set to 1 (structured). |
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Destination ID |
0 |
MMSI number of destination station. Not used. |
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Spare |
0 |
Not used. |
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Binary Data |
Designated Area Code |
10 |
Designated area code (DAC). Set to 366. |
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Function Identifier |
6 |
Function identifier. Set to 18. |
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Encrypted Payload |
Version |
3 |
Sequential number used to indicate the message version in steps of 1. 0 = test message = default; 1 – 7 = message version. Set to zero. |
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Message Linkage ID |
10 |
A source-specific random number, unique across recent binary messages with Message Linkage ID. Used to connect the additional information in this Text Message with another ASM. The Message Linkage ID and the source MMSI uniquely identify the sent message. 1 – 1023; 0 = not available. |
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Target Acquisition Source |
3 |
Type of Target. 0 = unknown = default; 1 = AIS, 2 = Radar, 3 = visual sighting; 4 = reported; 5 = other electronic surveillance, i.e. DSC, ECDIS, etc.; 6 -7 = reserved. |
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Target ID |
30 |
MMSI if type is Target Acquisition source=1 (AIS), Sender generated ID otherwise |
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TOI Status |
2 |
Designator for TOI Status 0 = cancel; 1 = active; 2 = being followed; 3 = being boarded. |
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Target Type |
3 |
Type of Target 0 = vessel = default; 1 = aircraft; 2 = submersible; 3-7 = reserved. |
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Target Description and Cargo |
8 |
Description of target type and cargo, see Appendix 3. |
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Interest |
8 |
Code to indicate what interest in vessel is. To be defined. Could be used as an 8- bit binary matrix, similar to ATON Status bits. TBD. |
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Binary Data |
Encrypted Payload |
Time of TOI Report |
UTC Hour |
5 |
UTC Hour of TOI report. 0 – 23; 24 = UTC hour not available = default; 25 - 31 = reserved. |
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UTC Min |
6 |
UTC Minute of TOI report. 0 – 59; 60 = UTC minute not available = default; 61 - 63 (reserved for future use). |
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UTC Sec |
6 |
UTC Second of TOI report. 0 – 59; 60 = UTC second not available = default; 61 - 63 (reserved). |
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Longitude |
28 |
Longitude in 1/10,000 min (+/-180 degrees, East = positive, West = negative - 2’s complement). 181 degrees = not available = default. |
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Latitude |
27 |
Latitude in 1/10,000 min (+/-180 degrees, East = positive, West = negative - 2’s complement). 91 degrees = not available = default. |
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SOG |
10 |
Speed over ground. Scale dependent on value of craft flag. Aircraft: 0 – 1000 kts (1 kt increments); 1001 = 1001 kts or higher; 1002 = not available = default; 1003 – 1023 = reserved. Vessel: 0 – 100.0 kts (0.1 kt increments); 1001 = 100.1 kts or higher; 1002 = not available = default; 1003 – 1023 = reserved. |
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COG |
12 |
Course over ground in 1/10 degree steps. 0 - 359.9 degrees; 3600 = not available = default; 3601 - 4095 = reserved. |
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Encryption Bit Padding |
95 |
Sufficient spare bits to ensure that the binary data is a multiple of 128 bits for block encryption (256). Set to zero. |
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Checksum |
16 |
16-bit CRC calculated as per EAIS Specification |
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Footer |
Spare |
4 |
Four extra bits to ensure the message ends on a byte boundary. Set to zero. |
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Communications State Selector |
1 |
0 = SOTDMA communication state follows 1 = ITDMA communication state follows |
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Communications State |
19 |
SOTDMA communication state (see ITU 1371-5 § 3.3.7.2.1, Annex 2), if communication state selector flag is set to 0, or ITDMA communication state (§ 3.3.7.3.2, Annex 2), if communication state selector flag is set to 1. |
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Total bits |
352 |
2 Slot Binary Message |
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