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.