AIS Application-Specific Messages

April 26, 2026 · View on GitHub

Published: 2025-01-20 Updated: 2026-04-26

Most AIS users know the standard position reports and static vessel data messages. AIS also supports Application-Specific Messages (ASM), which carry specialized structured data for weather, port operations, safety, inland waterways, and other domain-specific use cases.

What are application-specific messages?

Application-specific payloads are transmitted via:

message type 6: Addressed Binary Message
message type 8: Binary Broadcast Message

These messages are identified by:

DAC (Designated Area Code), which identifies the region or organization defining the format
FI (Function Identifier), which identifies the specific message type within that DAC

Examples:

DAC=001, FI=11 → UTC and Date Response
DAC=200, FI=10 → European inland ship static and voyage data
DAC=316, FI=1 → United States PAWSS family messages

IMO SN.1/Circ.289 international messages

The IMO circular SN.1/Circ.289 standardizes 24 international message types under DAC=001.

Weather and environmental data

FI=31: Meteorological and Hydrographical Data
FI=21: Weather Observation from Ship
FI=26: Environmental messages

These support transmission of wind, air pressure, wave height, salinity, ice conditions, and related observations.

FI=22, 23: Area Notice
FI=18, 19: Marine Traffic Signal
FI=25: Dangerous Cargo Indication
FI=14: Tidal Window

These messages support hazard warnings, traffic control, cargo awareness, and passage planning.

Port and vessel operations

FI=20: Berthing Data
FI=40: Number of Persons on Board
FI=27, 28: Route Information

Vessel information

FI=24: Extended Ship Static and Voyage Related Data
FI=0, 1: Text Description

Why application-specific messages matter

enhanced maritime safety through richer operational data
better port optimization and traffic coordination
improved environmental monitoring
better support for compliance and emergency response
inland waterway management beyond the standard deep-sea AIS profiles

Decoding ASMs with AISmessages

AISmessages supports ASM decoding directly from the parent binary AIS message. Decode NMEA sentences using NMEAMessageHandler or AISInputStreamReader, then cast the resulting AISMessage to access the embedded ASM.

Example: meteorological and hydrographical data

import dk.tbsalling.aismessages.ais.messages.AISMessage;
import dk.tbsalling.aismessages.ais.messages.BinaryBroadcastMessage;
import dk.tbsalling.aismessages.ais.messages.asm.ApplicationSpecificMessage;
import dk.tbsalling.aismessages.ais.messages.asm.MeteorologicalAndHydrographicalData;
import dk.tbsalling.aismessages.nmea.NMEAMessageHandler;
import dk.tbsalling.aismessages.nmea.messages.NMEAMessage;

import java.util.ArrayList;
import java.util.List;

public class WeatherDataExample {
    public static void main(String[] args) {
        String nmea = "!AIVDM,1,1,,A,85MwpKiKf:MPiQa:ofV@v2mQTfB26oEtbEVqh4j1QDQPHjhpkNJ3,0*11";

        List<AISMessage> decoded = new ArrayList<>();
        NMEAMessageHandler handler = new NMEAMessageHandler("EXAMPLE", decoded::add);
        handler.accept(new NMEAMessage(nmea));
        handler.flush();

        for (AISMessage aisMessage : decoded) {
            if (aisMessage instanceof BinaryBroadcastMessage binaryMessage) {
                ApplicationSpecificMessage asm = binaryMessage.getApplicationSpecificMessage();

                if (asm instanceof MeteorologicalAndHydrographicalData weather) {
                    System.out.println("Weather Report from MMSI: " + binaryMessage.getSourceMmsi());
                    System.out.println("Position: " + weather.getLatitude() + ", " + weather.getLongitude());
                    System.out.println("Wind Speed: " + weather.getWindSpeed() + " knots");
                    System.out.println("Air Temperature: " + weather.getAirTemperature() + " °C");
                    System.out.println("Wave Height: " + weather.getWaveHeight() + " m");
                }
            }
        }
    }
}

Example: inland waterway data

import dk.tbsalling.aismessages.ais.messages.asm.InlandShipStaticAndVoyageRelatedData;

if (asm instanceof InlandShipStaticAndVoyageRelatedData inland) {
    System.out.println("European Vessel ID: "
        + inland.getUniqueEuropeanVesselIdentificationNumber());
    System.out.println("Length: " + inland.getLengthOfShip() + " m");
    System.out.println("Beam: " + inland.getBeamOfShip() + " m");
    System.out.println("Ship Type Code: " + inland.getShipOrCombinationType());
    System.out.println("Draught: " + inland.getDraught() + " m");
}

Example: area notices

if (asm instanceof AreaNotice notice) {
    System.out.println("Notice Type: " + notice.getNoticeType());
    System.out.println("Start: " + notice.getMonth() + "/" + notice.getDay()
        + " " + notice.getHour() + ":" + notice.getMinute());
    System.out.println("Duration: " + notice.getDurationMinutes() + " minutes");
}

Example: unknown messages

if (asm instanceof UnknownApplicationSpecificMessage unknown) {
    System.out.println("DAC: " + unknown.getDesignatedAreaCode());
    System.out.println("FI: " + unknown.getFunctionalId());
    System.out.println("Binary Data: " + unknown.getBinaryData());
}

Example: processing a mixed stream

import dk.tbsalling.aismessages.AISInputStreamReader;
import dk.tbsalling.aismessages.ais.messages.BinaryBroadcastMessage;
import dk.tbsalling.aismessages.ais.messages.asm.ApplicationSpecificMessage;
import dk.tbsalling.aismessages.ais.messages.asm.MeteorologicalAndHydrographicalData;
import java.io.InputStream;

AISInputStreamReader reader = new AISInputStreamReader(
    inputStream,
    aisMessage -> {
        if (aisMessage instanceof BinaryBroadcastMessage binaryMessage) {
            ApplicationSpecificMessage asm = binaryMessage.getApplicationSpecificMessage();
            if (asm instanceof MeteorologicalAndHydrographicalData weather) {
                System.out.println("Wind: " + weather.getWindSpeed() + " kt at " + weather.getWindDirection() + "°");
            }
        }
    }
);

reader.run();

Supported messages in AISmessages

The repository README maintains the current support overview. The supported ASM set includes:

International (DAC=001)

Text Description (FI=0, 1)
UTC/Date Inquiry (FI=10)
UTC/Date Response (FI=11)
Tidal Window (FI=14)
VTS Generated/Synthetic Targets (FI=17)
Marine Traffic Signal (FI=18, 19)
Berthing Data (FI=20)
Weather Observation from Ship (FI=21)
Area Notice (FI=22, 23)
Extended Ship Static and Voyage Related Data (FI=24)
Dangerous Cargo Indication (FI=25)
Environmental (FI=26)
Route Information (FI=27, 28)
Meteorological and Hydrographical Data (FI=31)
Number of Persons on Board (FI=40)

Regional

DAC=200, FI=10: Inland Ship Static and Voyage Related Data

Real-world uses

port community systems
weather services
vessel traffic services
search and rescue
environmental monitoring