AIS Sentences

AIS Sentences (NMEA Sentences for AIS Communication) 📡⚓

In AIS (Automatic Identification System), sentences refer to NMEA (National Marine Electronics Association) 0183 formatted messages that AIS transceivers use to send and receive data. These sentences encode ship information, navigation status, and other maritime details.

🔹 Common AIS NMEA Sentences

AIS messages follow a structure like:

!AIVDM,1,1,,A,13aG;J0000OrTvLMrP9L4?vN0<05,0*7D

Each AIS sentence contains multiple fields separated by commas.

1. !AIVDM – AIS Data Message (Most Common)

Format:
!AIVDM,<Total>,<Number>,<Sequential Message ID>,<Channel>,<Data Payload>,<Checksum>

• Example:
  
  !AIVDM,1,1,,A,13aG;J0000OrTvLMrP9L4?vN0<05,0*7D

• Used For:

  • Sending AIS data from ships to receivers (e.g., vessel name, position, speed, etc.).

  • Received by base stations, satellites, or other ships.

2. !AIVDO – AIS Own Vessel Data Output

• Similar to AIVDM but used by a ship to broadcast its own AIS data.

Example:
!AIVDO,1,1,,A,13aG;J0000OrTvLMrP9L4?vN0<05,0*5A

• Used For:

  • Sending AIS position reports from own vessel to other AIS receivers.

3. !ABVDM – Base Station AIS Data Message

• Similar to AIVDM but sent from AIS base stations instead of ships.

Example:
!ABVDM,1,1,,B,13aG;J0000OrTvLMrP9L4?vN0<05,0*3E

• Used For:

  • Sending AIS data from shore-based stations to vessels.

4. !BSVDM – Satellite AIS Data Message 🛰️

• Used by satellites to send AIS data collected from ships.

Example:
!BSVDM,1,1,,B,402NjvQuh0t@j6L4J20H50000000,0*3C

• Used For:

  • Global vessel tracking via satellites.

🔹 AIS Sentences & Data Interpretation

Each AIS NMEA sentence encodes specific vessel and navigation data. For example:

AIS Data Type AIS NMEA Sentence Type Example Data

Vessel Position !AIVDM / !AIVDO Latitude, Longitude, Speed, Heading

Static Ship Info !AIVDM MMSI, Ship Name, Call Sign

AIS Base Station Data !ABVDM Shore station info

Satellite AIS Data !BSVDM AIS from satellites

Weather/Navigation !AIVDM Weather, Safety Broadcasts

🔹 Conclusion

AIS sentences, mainly !AIVDM, !AIVDO, !ABVDM, and !BSVDM, are NMEA 0183 messages used for vessel tracking and navigation. These messages are widely used in ship traffic monitoring, collision avoidance, and maritime surveillance.