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Mode-S/ADS-B (Dump 1090) Java Library

This library decodes ADS-B Messages and creates an easy to work with track object.

Message support status

Downlink Format Human Readable Supported Note
DF0 Short Air-Air Surveillance ✅
DF4 Surveillance, Altitude request ✅ Updates Altitude information + SPI (Ident)
DF5 Surveillance, Identity request ✅ Updates Callsign + SPI (Ident)
DF11 MODE S only all-call ✅ Broadcasts ICAO Mode-S address
DF16 Long Air-Air Surveillance ✅ Logs warning when ACAS RA is active
DF17 Extended Squitter (Most ADS-B Data) ⚠️ Partially supported, see DF17/18 status below
DF18 Extended Squitter/Supplementary (Ground) ⚠️ Partially supported, see DF17/18 status below
DF19 Extended Squitter Military ❌ Not supported at this stage
DF20 Comm-B Altitude ⚠️ Partially supported, see DF20/21 status below
DF21 Comm-B Identity ⚠️ Partially supported, see DF20/21 status below
DF24 Comm-B ELM ⚠️ Implemented basic sequence no decoding.

DF17/DF18 - Extended Squitter

DF17 is used for aircraft, while DF18 is used for other vessels (ground vehicles, static objects, ...)

Most features of the DF17/18 protocol have been implemented, some message lack support for specific fields.

Type Code Human Readable Supported Note
0 Airborne/Surface No altitude ✅
1 Aircraft Identification ✅
2 Aircraft Identification ✅
3 Aircraft Identification ✅
4 Aircraft Identification ✅
5 Surface Position ✅
6 Surface Position ✅
7 Surface Position ✅
8 Surface Position ✅
9 Airborne Position ✅
10 Airborne Position ✅
11 Airborne Position ✅
12 Airborne Position ✅
13 Airborne Position ✅
14 Airborne Position ✅
15 Airborne Position ✅
16 Airborne Position ✅
17 Airborne Position ✅
18 Airborne Position ✅
19 Airborne Velocity ✅
20 Airborne Position ✅
21 Airborne Position ✅
22 Airborne Position ✅
23 Test Message ✅
24 Surface System Status ❌ Not implemented yet
25 Reserved Message ✅
26 Reserved Message ✅
27 Reserved (Trajectory Change) ✅
28 Aircraft Status Message ✅ Priority mode A code (emergency) + TCAS/ACAS RA Broadcast
29 Target Status Message ✅ Partial support
30 Reserved Message ✅
31 Aircraft Operational Status ✅ Partial support

DF20/21 Comm-B

DF20/21 messages are replies to data requests from a radar station, you'll only receive these messages if Mode-S radar is actively requesting this information. You will only receive messages requested by the radar.

Message is structured as follows:

LSB |1----|6--|9----|14----|20-----------|33------------------------------------------------------|89-----------------------|
    | DF  |FS | DR  |  UM  |     AC      |                         MB                             |            AP           |
MSB |----5|--8|---13|----19|-----------32|------------------------------------------------------88|----------------------112|

LSB: Least Significant Bit (First bit) (inclusive)
MSB: Most Significant bit (Last bit) (Inclusive)

DF: Downlink Format
FS: Flight Status
DR: Downlink Request
UM: Utitlity Message
AC: Altitude Code (DF20: Altitude | DF21: Mode-A Code)
MB: Comm-B Message
AP: Address / Parity (Mode-S Address + Parity check)

The system uses BDS (comm-B Data Selected) code to determine the requested information. The radar station will send a request (UF20 / UF21) containing a reply ID. The reply ID is a used by the aircraft in the response. This means the reply by the aircraft does not contain the original BDS, without this info you have to guess which BDS is used.

You run through each BDS and pass the message to the decoder, if the message does not fit you assume it's not correct. Repeat this process until you have a match.

At this moment the coded logic has too many incorrect matches and thus decided to disable BDS guessing. We are actively looking for a fix, or at least the ability to enable this with an experimental flag. We hope with more BDS implemented the guessing accuracy will improve.

BDS Human Readable Supported Note
1,0 Data link capability report ❌ Detection implemented, decoding missing
1,7 Common usage GICB capability report ✅
1,8 Mode S services GICB capability report ❌
1,9 Mode S services GICB capability report ❌
1,A Mode S services GICB capability report ❌
1,B Mode S services GICB capability report ❌
1,C Mode S services GICB capability report ❌
1,D Mode S services GICB capability report ❌
1,E Mode S services GICB capability report ❌
1,F Mode S services GICB capability report ❌
2,0 Aircraft Identification ✅
2,1 Aircraft and Airline registration marking ✅️ Experimental
2,2 Antenna positions ❌
2,5 Antenna type ❌
3,0 ACAS Active resolution advisory ❌ Detection implemented, decoding missing
4,0 Selected vertical intention ✅️
4,1 Next waypoint details ❌ 9 Characters
4,2 Next waypoint details ❌ Waypoint lat/lon + crossing altitude
4,3 Next waypoint details ❌ Bearing, time and distance to waypoint
4,4 Meteorological routine air report ✅
4,5 Meteorological hazard report ✅
4,8 VHF Channel report ❌ Info on VHF 1/2/3 (frequency + status) & Guard status
5,0 Track and turn report ✅
5,1 Position report coarse ❌
5,2 Position report fine ❌
5,3 Air-reference state vector ✅
5,4 Waypoint 1 ❌ 5 Chars, ETA, Estimated level, time to go
5,5 Waypoint 2 ❌ 5 Chars, ETA, Estimated level, time to go
5,5 Waypoint 3 ❌ 5 Chars, ETA, Estimated level, time to go
5,F Quasi-static parameter monitoring ❌
6,0 Heading and speed report ✅
6,1 Priority/emergency status ❌
6,5 Aircraft operational status ❌
E,3 Transponder type/part number ❌
E,4 Transponder software revision number ❌
E,5 ACAS type/part number ❌
E,6 ACAS software revision number ❌
E,7 Transponder status and diagnostics ❌
E,A Vendor specific status and diagnostics ❌
F,1 Military application ❌
F,2 Military application ❌

Installation

This package is available through Maven Central

Pom

<dependency>
  <groupId>aero.t2s</groupId>
  <artifactId>mode-s</artifactId>
  <version>0.2.0</version>
</dependency>

Gradle

 compile('aero.t2s:mode-s:0.2.0-SNAPSHOT')

Usage

class Main
{
    public static void main(String[] args){
        ModeS modes = new ModeS("127.0.0.1", 30002, 52.0, 0.0);

        modes.onTrackCreated(track -> System.out.println("CREATED " + track.toString()));
        modes.onTrackUpdated(track -> System.out.println("UPDATED " + track.toString()));
        modes.onTrackDeleted(track -> System.out.println("DELETED " + track.toString()));

        // Get decoded Downlink messages
        modes.onMessage(message -> System.out.println("MESSAGE " + message.getClass().getSimpleName()));
        
        // Starts listening thread
        modes.start();
   
        // Get all tracks Map<String, Track>
        modes.getTracks();
    
        // Stop listening
        modes.stop();
    }
}

Using Aircraft Database

This library is compatible with OpenSky dataset.

In order to use the database version you can start ModeS plugin as follows:

class Main
{
    public static void main(String[] args){
        ModeSDatabase database = new ModeSDatabase(Path.of("./doc8643AircraftTypes.csv"), Path.of("./aircraftDatabase.csv"))
        ModeS modes = new ModeS("127.0.0.1", 30002, 52.0, 0.0);
    }
}

DF Messages only

If you don't need or want to use the track management feature you can also use this library without it.

class Main
{
    public static void main(String[] args){
        ModeSMessageHandler handler = new ModeSMessageHandler(52.0, 0.0);
        handler.onMessage((df) -> System.out.println(message.getClass().getSimpleName()));
        ModeS modes = new ModeS("127.0.0.1", 30002, handler);
    }
}

Contributing

You can contribute to this project by reporting/fixing bugs or implement a new packet.
We are always looking for help on this project.

License

This library is Apache 2.0 licensed. You can read the full license here.