Long-range automatic identification system broadcast message

msg_ID: 
27
Description: 
Class A and Class B "SO" shipborne mobile equipment outside base station coverage
Priority: 
1
Access scheme: 
MSSA
Communication state: 
N/A
Transmitted by: 
Mobile station

This message is primarily intended for long-range detection of AIS Class A and Class B “SO” equipped vessels (typically by satellite). This message has a similar content to Messages 1, 2 and 3, but the total number of bits has been compressed to allow for increased propagation delays associated with long-range detection. Refer to Annex 4 for details on Long-Range applications.
TABLE 84[1]

Parameter Number of bits Description
Message ID 6 Identifier for this message; always 27
Repeat indicator 2 Always 3
User ID 30 MMSI number
Position accuracy 1 As defined for Message 1
RAIM flag 1 As defined for Message 1
Navigational status 4 As defined for Message 1
Longitude 18 Longitude in 1/10 min (±180°, East = positive (as per 2’s complement), West = negative (as per 2’s complement)
181° (1A838h) = position older than 6 hours or not available = default)
Latitude 17 Latitude in 1/10 min (±90°, North = positive (as per 2’s complement), South = negative (as per 2’s complement)
91° (D548h) = position older than 6 hours or not available = default)
SOG 6 Knots (0-62); 63 = not available = default
COG 9 Degrees (0-359); 511 = not available = default
Position latency 1 0 = Reported position latency is less than 5 seconds; 1 = Reported position latency is greater than 5 seconds = default
Spare 1 Set to zero, to preserve byte boundaries
Total number of bits 96  
NOTE 1 – There is no time stamp in this message. The receiving system is expected to provide the time stamp when this message is received.
 
 


[1]   1 Nautical mile = 1 852 metres
    1 knot = 1 852 m/h