Ais Decoder (TypeScript)

Usage no npm install needed!

<script type="module">
  import aisDecoderTs from '';


AIS Decoder

The automatic identification system (AIS) is an automatic Tracking system used on ships and by vessel traffic services (VTS). When satellites are used to detect AIS signatures, the term Satellite-AIS (S-AIS) is used. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport.

Build Status

Ideal Node Version : 8.16.2

Tests : run npm test


  1. Position[0] format: !AIVDM, identifies this as an AIVDM packet (AIS format).
  2. Position[1] message_count: Messages counter (number of messages), sometimes the ais messages will be split over several messages.
  3. Position[2] message_id:
  4. Position[3] sequence_id: Sequential message, the current message number
  5. Position[4] channel: vhf channel A/B
  6. Position[5] payload: the ais data itself
  7. Position[6] size: number of bits required to fill the data

<format>,<message count>,<message id>,<sequence id>,<channel A/B>,<data>,<fill bits>

Important notes:

  • Ais payload is represented in a 6bits encoded string


  • constructor(AIS_Messages, safeMode)
    • AIS_Messages: Array of ais messages.
    • safeMode: set to false by default. when true the module will never throw an error (silent mode).
  • getResults() - return a collection of the parse messages
  • private decode(input: Array<any>, session: any): void - decode the raw ais messages
  • private validateRawMessage(input: string): boolean - validate if the raw messages

Command Line:

  • node dist/bin/parse <ais message> for example: node ./dist/bin/parse "!AIVDM,1,1,,A,13u?etPv2;0n:dDPwUM1U1Cb069D,0*24"

Running example:

  • npm run example


// new Decoder(Array<AIS_Messages>, safeMode<Boolean>)
import { Decoder } from '../lib/index';
const aisMessages:Array<string> = [
  '!AIVDM,2,1,0,A,58wt8Ui`g??r21`7S=:22058<v05Htp000000015>8OA;0sk,0*7B ',
const safeMode = false;
const aisDecoder_ex2 = new Decoder(aisMessages, safeMode);

// results will hold a collection of the parsed ais messages
const results = aisDecoder_ex2.getResults();


Bugs & PR's

  • If you find any bug please feel free to open an issue. PR are always welcome.