Message Type 1 — Class A Position Report

Same fields for types 1, 2 and 3. The active tab sets the message type bit.

Identity & status MMSI Nav status Repeat Maneuver

Position

Latitude ° S negative Longitude ° W negative

High accuracy (< 10 m) UTC second 60 = N/A

Motion SOG kn COG ° 360 = N/A Heading ° 511 = N/A ROT °/min blank = N/A

Advanced RAIM Radio status

Message Type 4 — Base Station Report

UTC date/time and base-station position. MMSI often starts with 00…

Identity MMSI Repeat EPFD High accuracy RAIM Radio status

UTC date & time Year Month 1–12 Day Hour 24 = N/A Minute 60 = N/A Second 60 = N/A

Position

Latitude ° Longitude °

Usually encodes as two NMEA fragments. Ship name max 20 characters.

Identity MMSI IMO number Callsign Ship name Ship type AIS version

Dimensions (m) To bow To stern To port To starboard EPFD Draught (m)

Voyage Destination ETA month 0 = N/A ETA day ETA hour 24 = N/A ETA minute 60 = N/A DTE not ready

Search-and-rescue aircraft report. MMSI often starts with 111… Altitude in metres; SOG in whole knots.

Standard Class B CS position report.

Identity & position

MMSI

Latitude ° Longitude °

High accuracy UTC second Repeat

Motion SOG kn COG ° Heading °

Class B flags CS unit Display equipped DSC Band flag Can accept Msg 22 Assigned mode RAIM Radio status

AtoN / buoy report. MMSI often starts with 99…

Identity MMSI Name Name extension Aid type Repeat

Position

Latitude ° Longitude °

High accuracy UTC second EPFD

Extent & flags To bow To stern To port To starboard Off position Virtual AtoN Assigned RAIM

Part A = ship name. Part B = type, vendor, callsign, dimensions.

Common MMSI Part Repeat

Part A Ship name

Coarse position broadcast (satellite / long-range). Speed max ~63 kn.

Identity & status MMSI Nav status Repeat

Position & motion

Latitude ° Longitude °

SOG kn ≤ 63 COG ° Position accuracy RAIM GNSS position