AIS VDM/VDO Decoder

Free online AIS VDM / VDO message decoder

ENTER ONE MESSAGE PER LINE.
MULTI SENTENCE MESSAGES HAVE TO BE ENTERED IN DIRECT SEQUENCE (viz. MSG 5, Msg 1-of-2, 2-of-2 )
Checksum (xor) failure is indicated where applicable.
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AIS NMEA VDM VDO Messages currently supported.

  • AIS Message 1,2,3 – AIS Class A Position Report
  • AIS Message 4 – Base station report
  • AIS Message 5 – AIS Class A Ship static and voyage related data
  • AIS Message 6 – Binary Data Addressed
  • AIS Message 6 – Generic
    • Sealite SL125 / 155 Apollo lantern – proprietary AIS AtoN (DAC,FI: regional / user configurable)
    • GLA Format for AIS Aids to Navigation Monitoring Message (DAC = 235 & 250; FI = 10)
  • AIS Message 8 – Binary Data Broadcast
  • AIS Message 8 – Generic
    • AIS AtoN Meteorological and Hydrographic data (DAC001,FI31) (IMO SN.1/Circ.289)
  • AIS Message 9 – Standard SAR aircraft position report
  • AIS Message 11 – Mobile UTC and date response
  • AIS Message 12 – Safety Related Addressed
  • AIS Message 14 – Safety Related Broadcast
  • AIS Message 18 – Class B/CS Position Report
  • AIS Message 19 – Extended Class B Equipment Position Report
  • AIS Message 21 – Aids To Navigation Report
  • AIS Message 24 – Class B/CS Static data report (Part A & B)
  • AIS Message 27 – Position report for long range applications

All supported messages are decoded irrespective of their checksum's (XOR).
However, checksum failures are indicated where applicable.

AIS MESSAGES – ITU-R M.1371-5

Msg ID Name Description Prio-rity Access scheme Communi-cation state M/B
1 Position report Scheduled position report; (Class A shipborne mobile equipment) 1 SOTDMA, RATDMA, ITDMA(1) SOTDMA M
2 Position report Assigned scheduled position report; (Class A shipborne mobile equipment) 1 SOTDMA(9) SOTDMA M
3 Position report Special position report, response to interrogation; (Class A shipborne mobile equipment) 1 RATDMA(1) ITDMA M
4 Base station report Position, UTC, date and current slot number of base station 1 FATDMA(3) (7), RATDMA(2) SOTDMA B
5 Static and voyage related data Scheduled static and voyage related vessel data report; (Class A shipborne mobile equipment) 4(5) RATDMA, ITDMA(2) N/A M
6 Binary addressed Binary data for addressed communication 4 RATDMA(10), FATDMA, ITDMA(2) N/A M/B
7 Binary acknowledgement Acknowledgement of received addressed binary data 1 RATDMA, FATDMA, ITDMA(2) N/A M/B
8 Binary broadcast message Binary data for broadcast communication 4 RATDMA(10), FATDMA, ITDMA(2) N/A M/B
9 Standard SAR aircraft position report Position report for airborne stations involved in SAR operations, only 1 SOTDMA, RATDMA, ITDMA(1) SOTDMA ITDMA M
10 UTC/date inquiry Request UTC and date 3 RATDMA, FATDMA, ITDMA(2) N/A M/B
11 UTC/date response Current UTC and date if available 3 RATDMA, ITDMA(2) SOTDMA M
12 Addressed safety related message Safety related data for addressed communication 2 RATDMA(10), FATDMA, ITDMA(2) N/A M/B
13 Safety related acknowledgement Acknowledgement of received addressed safety related message 1 RATDMA, FATDMA, ITDMA(2) N/A M/B
14 Safety related broadcast message Safety related data for broadcast communication 2 RATDMA(10), FATDMA, ITDMA(2) N/A M/B
15 Interrogation Request for a specific message type (can result in multiple responses from one or several stations)(4) 3 RATDMA, FATDMA, ITDMA(2) N/A M/B
16 Assignment mode command Assignment of a specific report behaviour by competent authority using a Base station 1 RATDMA, FATDMA(2) N/A B
17 DGNSS broadcast binary message DGNSS corrections provided by a base station 2 FATDMA(3), RATDMA(2) N/A B
18 Standard Class B equipment position report Standard position report for Class B shipborne mobile equipment to be used instead of Messages 1, 2, 3(8) 1 SOTDMA, ITDMA(1), CSTDMA SOTDMA, ITDMA M
19 Extended Class B equipment position report Extended position report for class B shipborne mobile equipment; contains additional static information(8) 1 ITDMA N/A M
20 Data link management message Reserve slots for Base station(s) 1 FATDMA(3), RATDMA N/A B
21 Aids-to-navigation report Position and status report for aids-to-navigation 1 FATDMA(3), RATDMA(2) N/A M/B
22 Channel management(6) Management of channels and transceiver modes by a Base station 1 FATDMA(3), RATDMA(2) N/A B
23 Group assignment command Assignment of a specific report behaviour by competent authority using a Base station to a specific group of mobiles 1 FATDMA, RATDMA N/A B
24 Static data report Additional data assigned to an MMSI
Part A: Name
Part B: Static Data
4 RATDMA, ITDMA, CSTDMA, FATDMA N/A M/B
25 Single slot binary message Short unscheduled binary data transmission (Broadcast or addressed) 4 RATDMA, ITDMA, CSTDMA, FATDMA N/A M/B
26 Multiple slot binary message with Communications State1 Scheduled binary data transmission (Broadcast or addressed) 4 SOTDMA, RATDMA, ITDMA SOTDMA, ITDMA M/B
27 Position report for long range applications Scheduled position report; (Class A shipborne mobile equipment outside base station coverage) 1 RATDMA N/A M
28-63 Undefined; Reserved for future use N/A N/A N/A N/A M

 

Terms - used in table above
  • N/A: Not Applicable
  • M/B:
    • M: transmitted by mobile station
    • B: transmitted by Base station.
  • FATDMA: Fixed Access Time Division Multiple Access
  • ITDMA: Incremental Time Division Multiple Access
  • SOTDMA: Self Organizing Time Division Multiple Access
  • RATDMA: Random Access Time Division Multiple Access

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